Method for manufacturing thin body warming devices

ABSTRACT

The present invention relates to the use of an exothermic composition having, as essential components, a water absorptive polymer and/or tackifier, carbon component and/or metal chloride and features that the product is as a whole ink-like or cream-like in a method of manufacturing an exothermic device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 08/676,851 filedJul. 8, 1996 now U.S. Pat. No. 6,436,128.

BACKGROUND OF THE INVENTION

The present invention relates to formation of a range of fluidexothermic compositions and of having these enclosed in what are knowngenerally as pouches by such a transfer, which now enable high-speedmanufacture of ultra-thin filled pouches, the filled composition beinguniformly distributable, and each of such exothermic pouches being thin,soft and flexible and excelled in touch in use because of the fluidfeature of, e.g., the transferred exothermic composition which can bepacked in a mating bag partly or entirely fixed thereto, and theinvention also relates thereto.

DESCRIPTION OF THE RELATED ART

In recent years, disposable flat body warmers such as exothermic deviceshaving an exothermic composition enclosed in a flat pouch made of agas-permeable or gas-tight filmy or thin covering material are widely inuse.

Some disposable body warmers have an adhesive layer formed on onesurface thereof to be applied directly or through underwear to the skinand also proposals have been made having a wet compress agent containedor carried therein for use as a wet compress or having a medicationcontained or carried therein for use as a skin absorbable medication(see Japanese Patent laid-open Publication No. 2-149272).

As a manufacturing method for such exothermic devices, generally adoptedare such methods as having a given exothermic composition deposited in agiven region of the substrate and a gas-permeable cover placed thereon.This is followed by sealing the edges by heat-sealing or bondage by theuse of a hot-melt adhesive.

Exothermic devices thus manufactured have the exothermic reactioninhibited before use, hence the exothermic composition is in thegas-tight outer bag as they are stored or distributed.

As conventional exothermic compositions were known, besides metal powderand water essential for an exothermic reaction, carbon components suchas carbon or active carbon are known for enhancing the exothermicreaction, metal halides for successive progress of the exothermicreaction through destruction of a surface oxide film of metal powder andfurther water-retainers such as wood flour.

As a method of depositing the powdery composition, there are knownalternative methods of moving the substrate intermittently anddepositing the powdery exothermic composition when the substrate isstopped and moving the exothermic composition discharging port at thesame speed as the substrate to deposit the powdery exothermiccomposition on the moving substrate. For enhancing the manufacture,however, the latter method is preferred.

When the exothermic composition is formed powdery as in the past, thepowdery exothermic composition is compounded in an optimum state suchthat the exothermic reaction, namely the oxidation reaction, is likelyto occur. Moreover, it is powdery and highly porous, high in specificsurface area and is extremely good in contact with air, thus causingimmediate starting of an oxidation reaction upon contact with air.

If an oxidative reaction with air, i.e., exothermic reaction, shouldtake place during compounding exothermic compositions at a proper ratioand during the period between manufacture of the exothermic compositionsand completion of manufacture of the exothermic device, this resultingin loss due to an exothermic reaction of an exothermic composition aswell as lowering of the quality of the exothermic compositions andgiving rise to various problems such as coagulation of compositionsresulting from the exothermic reaction. Specifically, lowering yield dueto removal of coagulants, increased difficulty in handling, growingcomplications of machine maintenance, more strict limitation of amachine's per-day operating hours and a worker's working hours,increased difficulty of treatment or disposal of coagulants.

If the exothermic composition is powdery, oxidation reaction with airtakes place after manufacture of an exothermic device and before sealingthe resulting exothermic device in the gas-tight outer pouch, thisresulting in fatal defects such as lowering of the quality of anexothermic device as well as of its reliability.

For prevention of an oxidation reaction of such exothermic compositions,it is possible to make the mixer gas-tight and replace the air withnitrogen before proceeding to uniform mixing of the exothermiccompositions. This way, however, the mixer not only becomes morecomplicated and more expensive, this also results in increased costs ofthe exothermic compositions and exothermic devices,

Another method of depositing the exothermic composition when thesubstrate is stopped in the course of its intermittent movement has adrawback of the manufacturing speed getting lower, for the substratestops and restarts frequently.

Still another method of depositing the exothermic composition onto thesubstrate moving at a constant speed through the deposition port beingmoved at the same speed enables increasing the manufacturing speedbecause the substrate is seldom stopped and restarted.

Since, in this case, a complicated mechanism becomes necessary formoving the deposition part for the exothermic composition at the samespeed as the substrate and, worse, the exothermic composition ismoistened by addition of water and, being powdery, is less frequent,there are many problems such as a strict limit for the speed of movingthe mechanism, decreased reliability due to poor filling property of theexothermic composition, increased scatter of the filling rate of theexothermic composition and eccentricity of the exothermic composition inthe pouch.

Although the exothermic composition is moistened by addition of water,the water content is low and proper for exothermic reaction, hence it ispowdery and less liquid and it is extremely difficult to have ituniformly distributed in a predetermined region of the substrate.

Although the distribution of the exothermic composition is not uniformto some extent by, e.g., a roller as it is sealed with a coveringmaterial thereon, the distribution of the exothermic composition tendsto be shifted toward a direction from which the pouch is sent. Hence, inorder to increase the distribution of the exothermic composition wherethe pouches are sent, it is necessary to make the exothermic devicethicker and eliminate distribution error by shaking it by hand beforeuse.

Hence, the exothermic devices as a whole become thicker to several mm,its feel becomes stiff and disagreeable and, worse, its softness isdeteriorated with an increasing difficulty to fit the complicatedcurvature of the body surface with failure to fit small curvatures. Alsodeteriorated are prolongation and stretching behaviors, this resultingin failure to readily follow movement of the body surface and givingproblems of an increased stiff feel, unpleasant feel or the like.

In order to put an exothermic device in a shoe to produce warmth, it isessential to try to have it thinner but in this respect the conventionalexothermic devices which are several mm thick are by far unsatisfactory.

Especially the conventional disposable body warmers, which have filledtherein powdery exothermic composition, are not constant in thicknesswith the exothermic composition shifting therein and, when some thereofis immovably fixed to the body surface, non-constant distribution ofexothermic temperature can possibly cause a burn.

In recent years, popularized products have been arranged to preventoff-center displacement in any direction but to date there has beenestablished no measure against displacement in any direction in any ofthe manufacturing processes, transport stage and distribution stage.

When the exothermic composition is stored in an outer pouch (storagepouch), the exothermic device has its inside undecompressed and in thetransfer stage the exothermic composition is movable or shiftable in theexothermic device. Also for ensuring safety, it is important to have thepouch's thickness kept uniform and have the temperature distributionconstant and with those having the exothermic decomposition shiftedoff-center it is a current practice to be returned as unfit products inthe distribution stage or exchanged when the consumer demands. Thus itis extremely important to ensure uniformity of thickness of theexothermic composition in the transport stage.

In Japanese Patent Laid-Open Publication No.62-347 there is proposed amethod of fixing an exothermic composition by an adhesive. In practicalmanufacture, however, it is almost impossible to bond a powderyexothermic composition to the inside of the exothermic pouch and, evenif it is feasible, the bonding strength is lowered and perfect fixing isnot feasible, the exothermic device is subject to separation or becomesplate-like in a user's feel. Worse, coexistence of an adhesive agentinterferes with contact between the exothermic composition and air, thisresulting in temperature unevenness and scattering of temperature, andlack of utility.

Hence, in order to solve the above-noted technical problems, theinventor has made intensive studies about exothermic devices forprevention of various problems such as loss of the exothermiccomposition due to exothermic reaction at the time of manufacture,lowering the quality of the exothermic composition and coagulationthereof to thereby enable high-speed manufacture of ultra-thinexothermic devices, also having such additional features as preventionof movement and off-center displacement of the exothermic composition bydistribution thereof in the pouch and fixing therein and preclusion ofexcessive exothermic reaction of the exothermic composition as far aspossible.

As the result, it turned out that the exothermic principle of disposablebody warmers is generation of heat taking place when metal powder isoxidized and that this oxidation reaction, namely, an exothermicreaction, has its reaction time largely dependent upon the presence ofwater.

In order to enhance this exothermic reaction, quite important is thepresence of proper moisture, not too high or too low degree thereofwhich markedly retards such a reaction. The presence of proper moistureenables balancing of water with air (oxygen) supply to metal powder tothereby enable progress of the oxidation reaction, namely, exothermicreaction, at the highest reaction time.

Too little water results in shortage of water required for a reaction inthe presence of ample air, while too much water retards the reactionwith the excessive moisture forming a barrier against a supply of air tometal powder.

Through such studies the inventor discovered that ultra-thin exothermicdevices are extremely easy to laminate by screen printing, coating orthe like and can be manufactured at high production when the exothermiccomposition is prepared to be fluid.

The inventor also discovered that such thickened exothermic compositioncan be uniformly distributed in the pouch and that when the fluidexothermic composition is laminated on paper including thin paper forhousehold use such as a foamed film sheet, tissue paper and towel paperand thick papers such as cardboard and corrugating medium thereof(hereinafter referred to as papers), nonwoven fabric, woven cloth or aporous film sheet, this fluid exothermic composition with its highpenetration and anchoring capability gets into the pores of such film orsheet to be safe from movement or displacement in any directionthereafter.

Further, the inventor discovered that, especially when such film orsheet has water-absorbency and the exothermic composition is laminatedthereon or when a water-absorptive layer is formed on the above-notedfilm or sheet and the fluid exothermic composition is laminated thereon,a whole or a part of the exothermic composition becomes more readily andsecurely fixed to the forming film or sheet, papers, nonwoven fabric,woven cloth or porous film or sheet or the water-absorptive layer formedthereon and thus its later movement or displacement in any direction isprecluded.

The inventor also discovered that, when the exothermic composition isformed as a fluid, the surface area becomes markedly less than that ofthe powdery exothermic composition, this resulting in strict limitationof contact with air and marked suppression of the oxidation reactionwith air.

Further, the inventor discovered that in the fluid exothermiccomposition excessive moisture or free moisture and/or water-containinggel covers the metal powder and forms an air barrier layer, this, too,resulting in extreme stability of the exothermic composition in the air.

In this case, where water is excessively incorporated in the exothermiccomposition, as in the case of fluid exothermic composition, theexcessive moisture functions as a barrier layer, this further suppressesthe exothermic reaction (oxidation reaction) with air and contributes tofurther improvement of stability.

Meanwhile, in the fluid exothermic composition it is not absolutelynecessary to incorporate water excessively and relatively less watercontent will do as in the case of the fluid exothermic composition. Insuch a case free moisture and/or water-containing gel (water-containing)covers the metal powder and functions as a gas-barrier layer, hence itsstability in the air is improved.

As in the case of a deoxidant containing an excessive amount of water,excessive moisture is absorbed by at least one of the backing, coveringmaterials and water-absorptive materials applied to either or both sidesof the fluid exothermic composition. In the case of the fluid exothermiccomposition, too, a part of free moisture and/or water-containing gel isabsorbed by at least one of the backing, covering material orwater-absorptive material applied to either or both sides of the fluidexothermic, this resulting in loss of the barrier, and the exothermiccomposition, now porous, is in good contact with air and the exothermicreaction proceeds smoothly.

Therefore, there is scarcely any oxidation reaction, namely exothermicreaction, during compounding of the exothermic composition and in thesteps of manufacture of fluid exothermic composition, lamination thereofon the substrate by printing, coating or the like and manufacture ofexothermic devices by covering the laminate with a proper material,hence loss of the exothermic composition with progress of an exothermicreaction and deterioration of the quality of the exothermic compositionand coagulation of the exothermic composition is precluded. Hence, thereaction yield and handling behavior are improved, machine maintenancebecame easy and limitations about machine's per-day working hours andworker's working hours were totally removed.

When the exothermic composition is fluid, there can scarcely be anyoxidation reaction with air in the course of manufacture of exothermicdevices until sealing thereof in a gas-tight outer pouch, hence thequality of the exothermic device is stabilized and its reliability isimproved.

Thus, the inventor discovered that, since the fluid exothermiccomposition is stabilized in the air, it is not necessary to make themixer gas-tight and it is neither necessary to replace air in the mixerwith nitrogen, hence a simple mixer is enough and the exothermiccomposition and exothermic device can be manufactured at low costs.

When, as mentioned above, the exothermic composition used is fluid,screen printing or transfer and lamination by coating or the like areextremely easy and ultra-thin exothermic devices can be manufactured ata high output. Moreover, the exothermic composition can be distributedinside a pouch uniformly, and movement and displacement in any directionof the exothermic composition during use or handling can be prevented.

The inventor discovered that the exothermic device can be made extremelythin by printing such as screen printing or by a lamination method suchas coating and, further, since the per-hour exothermic reaction rate islowered as the exothermic device is made thinner, excessive exothermicreaction of the exothermic device can be precluded.

The inventor discovered that by having an aqueous viscous solution of awater absorber laminated on a pouch of foam film, sheet, paper, nonwovenfabric or porous film or sheet by impregnation, scattering, kneading,printing, coating or the like and subsequent drying or by firstimparting water absorbency by having a water absorber contained in orcarried by the pouch by pressing, kneading or the like and then havingthe fluid exothermic composition transferred or laminated thereon byscreen printing, coating or the like. This way, the step of throwing-inpowder can be eliminated and the plant control meeting the GMP standardsto be applied in the near future to manufacture of medical instrumentsand medicines will become readily feasible.

The inventor also discovered that when the excessive moisture or freemoisture or a part of water in a water-containing gel is absorbed by atleast one of the water-absorbing materials is applied to either or bothsides of the fluid exothermic composition, the barrier layer iseliminated and at the time of use, the exothermic composition is porousand in good contact with air, thus resulting in excellent exothermicproperties.

The present invention has been completed on the basis of the technicalknowledge described above, and is aimed at preventing generation of dustin the course of manufacture of exothermic devices, at eliminating lossdue to exothermic reaction and precluding lowering of the quality of theexothermic composition and coagulation of the exothermic composition,uniform distribution of the exothermic composition through adoption ofprinting and transferring methods such as screen printing and coating,attaining a high precision of measuring the thickness and distributionof the exothermic composition for accomplishing an improved quality ofthe product and also facilitating high-speed manufacture of ultra-thinexothermic devices, transfer and lamination of the exothermiccomposition on water absorptive substrate or covering material or on awater-absorbing layer for uniform distribution and fixing of theexothermic composition and also for ensuring against movement anddisplacement in any direction of the exothermic composition.

Another object of this invention is to make a pouch water-absorptivewith a viscous aqueous solution of a water absorber by impregnation,spraying, kneading, printing or coating (lamination) and subsequentdrying or with a water absorber by pressing or kneading to be containedtherein or carried thereby, this followed by transfer or lamination ofan exothermic composition, this allowing elimination of the step ofthrowing-in powder and plant control meeting GMP standards to be appliedin the near future to manufacture of medical instruments and medicineswill become readily feasible.

SUMMARY OF THE INVENTION

The fluid exothermic composition according to the present invention(hereinafter referred to as invented composition) features, foraccomplishment of the above-described objects, having an exothermicsubstance, water-absorptive polymer and/or tackifier, carbon componentand/or metal halide and water as essential components, and features tobe generally fluid.

The exothermic device of the invention (hereinafter referred to asinvented exothermic device) is, for accomplishment of theabove-described object, made up of the invented composition laminatedand sealed in a thin pouch, at least part of the pouch is gas-permeableand a part of water of the invented composition noted above is absorbedby the aforementioned thin pouch.

The manufacturing method for the first exothermic device of theinvention (hereinafter referred to as invented method for the firstexothermic device) comprises, for accomplishment of the above-describedobject, the steps of preparing a fluid exothermic composition,laminating the fluid exothermic composition on at least a part of a filmof or a thin sheet of substrate, placing a film of or a thin sheet ofcovering material so as to cover said fluid exothermic composition. Atleast, either the substrate or the covering material or a part thereofis gas-permeable.

The manufacturing method for the second exothermic device of theinvention (hereinafter referred to as invented method for the secondexothermic device) comprises, for accomplishment of the above-describedobject, the steps of preparing a fluid exothermic composition,laminating the fluid exothermic composition on at least a part of a filmof or a thin sheet of substrate, laminating or scattering at least onecomponent selected from the group consisting of an iron powder, a carboncomponent and a water absorptive agent on a surface of the fluidexothermic composition, placing a film of or a thin sheet of coveringmaterial so as to cover the fluid exothermic composition and theselected component. At least either the substrate or the coveringmaterial or a part thereof is gas-permeable.

The manufacturing method for the third exothermic device of theinvention (hereinafter referred to as invented method for the thirdexothermic device) comprises, for accomplishment of the above-describedobject, the steps of preparing a fluid exothermic composition,laminating the fluid exothermic composition on a film of or a thin sheetof substrate, placing a film of or a thin sheet of covering material soas to cover the fluid exothermic composition, putting together thesubstrate and the covering material to obtain a laminae by a viscosityof the fluid exothermic composition, and stamping out the laminate intoa predetermined shape. At least either the substrate or the coveringmaterial or a part thereof is gas-permeable.

Hereinafter the invented composition, the invented exothermic device andthe invented methods 1 to 3 will be described in detail.

The invented composition here is not meant to be a conventional powderyone but an exothermic composition made as a fluid.

Further, this invented composition is composed of components capable ofentering into exothermic reaction with oxygen in the air, and there isno particular limitation as long as it is a fluid and changes shape whensubjected to an external force.

Specifically, the invented composition is obtainable through adjustmentof the mixing ratios for water, water-absorptive polymer and/ortackifier and other components.

The invented composition is formed as a fluid, this accounting for thevarious advantages described below.

Since the invented composition is fluid, printing is feasible by manyknown methods such as thick-film printing, gravure printing, offsetprinting, screen printing and spray printing, transfer or lamination isreadily feasible by the use of a head coater, a roller or an applicator,ultra-thin invented exothermic devices may as well be manufactured at ahigh speed, readily transferrable and laminatable and, further, it ispossible to have the invented composition uniformly distributed in apouch.

When this invented composition is transferred or laminated onto a foamfilm or sheet, paper, nonwoven or woven fabric or porous film or sheet,this invented composition being fluid has a high penetrating andanchoring capability and gets into pores of the film or sheet to staythere and is no longer movable or displaceable; the specific area ofcontact with air is extremely small and with the air supply diminished,penetration and anchoring capability gets into the pores of the film orsheet to be restricted from movement or displacement, the area forcontact with air is extremely small and the air supply is thusdiminished, there is scarcely any chance for progress of oxidationreaction.

In such a case, especially where such film or sheet is absorbent and theinvented composition is laminated thereon, the same is done afterforming a water-absorptive layer, hence the whole or a part of theexothermic composition is more securely held by the foam film or sheet,paper, nonwoven fabric or porous film or sheet and also by thewater-absorbent layer, this resulting in less chance for removal ordisplacing of such coating. When lamination is made by screen printingor coating, this exothermic composition can be made extremely thin andsince the per-hour exothermic reaction rate decreases with decreasingthickness of the exothermic device, excessive progress of the exothermicreaction is retarded, but, since the invented composition is fluid andthe coated thickness is small, removal or displacement of the formedexothermic coating is hardly feasible.

When the viscous aqueous solution of water absorber is laminated on apouch of foam film or sheet, paper, nonwoven fabric, woven cloth orporous film or sheet by impregnation, spraying, printing or coating(lamination) and subsequent drying or by pressing or kneading awater-absorber to have it contained in or carried by a pouch of sheet,this is followed by transfer or lamination of the invented composition,this allowing elimination of the step of throwing-in powder and plantcontrol meeting GMP standards to be applied in the near future tomanufacture of medical instruments and medicines will become readilyfeasible. As the above-noted water absorber is mainly used, awater-absorptive polymer or tackifier will be described later.

Since the invented composition is fluid with the water content of theexothermic composition and with the ratios of water-absorptive polymer,and/or tackifier properly adjusted, transfer or lamination by printingor coating is extremely easy and manufacture of ultra-thin exothermicdevice can be made at a high speed. Moreover, since the excessivemoisture acts as barrier, the air feeding rate decreases untilsubstantial stopping of the exothermic reaction, this resulting infurther stabilization of moisture in the air, which is preferred forreduced loss by exothermic reaction at the time of manufacture and alsofor increased safety from deterioration of the exothermic composition aswell as from coagulation thereof.

In this case, when the excessive moisture or free moisture or a part ofwater in the water-containing gel is absorbed by the pouch material,i.e., substrate and/or covering sheet, loss of the barrier layersresults, a further merit being absorption of water by the pouch and theresultant increased porousness of the invented composition, whichenhances contact with air.

In the invented exothermic composition, when the exothermic substancewith water-absorbing polymer and/or tackifier, carbon content and/ormetal halide and water as essential components has its viscosityadjusted to be fluid, the composition being: water-absorptive polymer in0.1 to 7.5 parts by weight and/or tackifier by weight in 0.1 to 10 partsand carbon component in 1.5 to 20 in parts by weight and/or metalchloride in 1 to 10 parts by weight as essential components per 100 inparts by weight, there mixed with further addition of water for thewhole to be fluid.

In this case, for preparation of the invented composition, the solidcomponents alone are thrown into a mixer and after uniformly mixingthem, water and/or aqueous solution of the metal halide may be added forpreparation of a fluid liquid or alternatively all of these exothermiccomponents may be mixed in the mixer to produce a fluid.

In case that water is in excess, there is no particular limitation aboutthe mixer for such components as long as it is capable of uniform mixingbut in the case of a fluid exothermic composition with a relatively lesswater content, the kneading apparatus such as a kneader or mixer ispreferred for the case of a fluid formation of exothermic compositionand, moreover, the surface of the exothermic composition is easilycovered by free moisture or water-containing gel.

As mentioned above, the invented exothermic composition is formed as afluid but it is desirable to have its viscosity (at 20° C.) measured bythe method described below generally in a range of 1,000 to 7,500,000cps, for if it is less than 1,000 cps, there results deterioration oftransferability of the exothermic composition such as printing orcoating, extreme excess of water resulting in shortage of the quantitiestransferable of other components, whereby the time of exothermicreaction is shortened due to extreme excess of water, this resulting inshortage of transferable quantities of other components, oozing of theexothermic composition beyond the predetermined region on the substrateor necessity of having a large amount of water absorbed by the substrateand the like, this, in turn, resulting in the necessity of using asubstrate etc. of special structure or of complicating the structure ofthe exothermic composition, while, if it is in excess of 7,500,000 cps,it is not preferable, either, for deterioration of transferabilitycausing scatter of transferred quantities or possibility of theexothermic reaction taking place in the surface. For these reasons, itis preferable to have this range from about 1,000 to about 6,500,000cps, more preferably from about 50,000 to 5,500.000 cps.

By viscosity it is here meant, when it is less than 2,000,000 cps., thevalue measured at 20° C. by the use of a viscosimeter BH-type(manufactured by TOKIMEC INC.), a #7 rotor (2 rpm.) and a beaker (85 φ)in inside diameter), and if it is in excess of 2,000,000 cps., is avalue measured at 20° C. by the use of a R110-type viscosimeter (RE110Usystem, Detection Head RE100U Controller RC100A, manufactured by TokiSangyo K. K.) and an SPP rotor 0.2 rpm (D=0.4 (1/S)).

The viscosity is here meant a value of what is transferred or laminated.

The components of the invented composition include, besides exothermicmaterials essential for exothermic reaction, namely water,water-absorptive polymer and/or tackifier and the like, carboncomponents such as carbon and active carbon for enhancing generation ofheat and/or metal halide for destruction of the superficial oxide filmof metal powder and successive occurrence of the exothermic reactionand, besides such essential components, inorganic or organic waterretainer, pH adjuster, surface active agents for enhancingdispersibility, defoaming agent, etc. are added, as desired.

The compounding ratio of the invented composition, although it dependson the kind of the water-absorptive polymer and tackifier, the kind ofexothermic materials and carbon components and the kind of metal halide,it is generally preferred to be in 0.1 to 7.5 parts by weight ofwater-absorptive polymer, in 0.1 to 10 parts by weight of tackifier, in1.5 to 20 parts by weight of carbon component and in 1 to 10 parts byweight of metal halide, and water is added to this mixture to make thewhole a fluid. In this case, the required quantity of metal halide isdissolved or dispersed in water and adding the same to a mixture ofwater-adsorptive polymer and/or tackifier and carbon components and/ormetal halide for the whole to be fluid.

In this case, instead of adding water or an aqueous solution or aqueousdispersion of metal halide, it is possible to add proper amount of waterto the aforementioned solid components and uniformly mixing the wholefor preparation of a product of the invented composition.

In this case, too, as in the previous case, it is preferred to have itsviscosity (20° C.) generally in a range of 1,000 to 7,500,000 cps. asmeasured by the method described above.

In the invented composition, as mentioned above, the desired exothermicproperty is obtainable even if it is composed of water, water-adsorptivepolymer and/or tackifier, exothermic substance, carbon components andmetal halide but, improvement of further temperature stability andlengthening of the time of exothermic reaction it is preferable tofurther add inorganic or organic water-retainer, pH adjuster, surfaceactive agents for improving dispersibility and defoaming agents formaking the whole a fluid.

That is, the exothermic composition includes 0.1 to 7.5 parts by weightof water-absorptive polymer and/or 0.1 to 10 parts by weight of metalhalide per 100 parts by weight of exothermic substance. Mixed in 100parts by weight of this exothermic composition are at least one of 0.5to 10 parts by weight of inorganic or organic water-retainer, 0.1 to 5parts by weight of pH adjuster, 0.1 to 5 parts by weight of surfaceactive agent for improving dispersibility, and 0.1 to 5 parts by weightof defoaming agent. In the present invention, water is added to thismixture so that the exothermic composition becomes a fluid. Of these,most preferred is metal halide, the required quantity of which may bedissolved or dispersed in water, added to the aforementioned mixture andthe whole is made fluid, this being particularly excellent in exothermicproperty. Thus, instead of mixing the solid components uniformly andthen adding water, aqueous solution or dispersion of metal halide, aproper amount of water may as well be added to the aforementioned solidcomponents and the invented composition is obtainable by uniform mixing.

In this case, too, as in the above-described case, the inventedcomposition is generally preferred to be 1,000 to 7,500,000 cps. inviscosity (20° C.) as measured by the above described method.

In the invented composition, the cited water-absorptive polymers arehigh polymers capable of absorbing a large amount of water or aqueoussolution of metal halide smoothly, specific examples thereof being oneor a combination of two or more of starch-polyacrylonitrile copolymerdisclosed in Japanese Patent Publication No. 49-43395, crosslinkedpolyalkylene oxide disclosed in Japanese Patent Publication No.51-39672, vinylester-ethylene-type unsaturated carboxylic copolymersaponificate disclosed in Japanese Patent Publication No. 53-13495,self-crosslinked polyacrylic salt obtained by reverse phase suspensionpolymerization disclosed in Japanese Patent Publication No. 54-30710, areaction product of polyvinyl alcohol polymer and cyclic anhydridedisclosed in Japanese Patent Laid-Open Publication No. 54-20093,polyacrylic salt crosslinked compound disclosed in Japanese PatentLaid-Open Publication No. 59-84305, N-vinylacetoamide crosslinkedcompound (water-absorber having a water-absorptive ability) (NA-010manufactured by Showa Denko K. K.). These may further be treated with asurface active agent and it is also possible to add surfactant theretofor improved hydrophilic property. Some of these hydrophilic polymersare capable of absorbing water or aqueous solution of metal halide forimparting viscosity but they mainly have a function of absorbing a largeamount of water or aqueous solution of metal halide smoothly.

A commercially available product may be used as a water absorptivepolymer. Examples thereof include Sanwet IM-300, Sanwet IM-300 MPS,Sanwet IM-1000, Sanwet IM-1000MPS, Sanwet IM-5000 and Sanwet IM-5000MPSmanufactured by Sanyo Kasei K. K., Aquakeep 4S and Aquakeep 4SHmanufactured by Seitetsu Kagaku K. K., Sumikagel NP-1020, SumikagelNP-1040, Sumikagel SP-520 and Sumikagel N-1040 manufactured by SumitomoKagaku K. K., KI Gel 201-K and KI Gel 201-F2 manufactured by Kurare K.K., and Arasoap 800 and Arasoap 800F manufactured by Arakawa Kagaku K.K.

Of such commercially available water-adsorptive polymers, particularlypreferred are Sanyo Kasei K. K.'s Sanwet IM-300MPS, Sanwet IM-1000MPSand Sanwet IM-5000MPS, Sumitomo Kagaku K. K.'s Sumikagel NP-1020 andSumikagel NP-1040, Kurare K. K.'s KI Gel 201-K and KI Gel 201-F2 andArakawa Kagaku K. K.'s Arasoap 800F.

As tackifiers for the invented composition are mainly used substancesabsorbing water or aqueous solution of metal halide for increasing theirconsistency or imparting thixotropy such as bentonite, polyacrylate suchas stearates and sodium polyacrylate, gelatin, polyethylene oxide,polyvinyl alcohol, polyvinyl pyrrolidone, gum arabic tragacanth gum,locust bean gum, gua gum, alginates such as sodium alginate, pectin,carboxyl vinyl polymer, dextrin, a-starch , starch flour-type waterabsorber such as starch flour for processing, carrageenan,polysaccharide-type tackifiers such as agar, CMC,cellulose-derivative-type tackifiers such as ethyl cellulose acetate,hydroxy ethyl cellulose or hydroxy propyl cellulose, acryl sulfonicacid-type high-polymers (such as CS-6HS manufactured by Nippon ShokubaiK. K.), water-soluble cellulose ether and poly-N-vinyl acetamide, eitheralone or in combination of two or more. These are also treated with asurface active agent or mixed therewith for improvement in hydrophilicproperty. Such tackifiers are used mainly for absorbing water or aqueoussolution of metal halide for increasing consistency or impartingthixotropy.

As specific examples of the aforementioned cellulose ethers may be citedmethyl cellulose with cellulose etherified with methoxyl group (such asMetrose SM15, Metrose SM25, Metrose SM400 and Metrose SM4,000manufactured by Shin'etsu Kagaku Kogyo K.K.), hydrozy propyl methylcellulose with cellulose etherified with hydroxy propoxyl group (such asMetrose 60SH-50, Metrose 60SH-4,000, Metrose 90SH-4,000, Metrose90SH-30,000, Metrose 90SH-100,000 of Shin'etsu Kagaku Kogyo K. K.),water-soluble cellulose ether like hydroxyethylmethyl cellulose etherwith the cellulose contained etherified by hydroxyethoxyl group (such asMetrose 60SH-50, Metrose 60SH-4,000, Metrose 90SH-4,000, Metrose90SH-30,000, Metrose 90SH-100,000) and water soluble cellulose etherssuch as Cerogen EP, Cerogen BSH-12, Sesuka MC, Sesuka MHEC abd SesukaMHPC manufactured by Daiichi Kogyo Seiyaku K. K.

When an aqueous solution of this water-soluble cellulose either isheated to a predetermined temperature (tackiness-induced temperature),it results in increase of viscosity, but if heating is continued beyondthis temperature, release of adsorbed water causes gelation (hereinaftercalled as phenomenon of tackiness-induced gelation), this resulting inreleasing of water for formation of a moisture barrier for inhibitingthe exothermic reaction, while, if the formed gel is cooled, the initialstate is restored through adsorption of water.

The tackiness-induced temperature of water-soluble cellulose eitherdepends on the kind of the etherifier, substitution ratio, the molecularweight of the cellulose, the concentration of the solution when it isadded as solution, the kind and amount added (concentration) of anyother additive, if any, and also heating/cooling rates. Hence, whenwater-soluble cellulose ether is used as a tackifier, the maximumexothermic temperature can be properly determined through proper actionof the kind of the etherifier used, the substitution ratio, themolecular weight of the cellulose, the solution's concentration and thekinds and dosages (concentrations) of other additives for controllingthe heating and cooling rates.

With 2% by weight of aqueous solution of, for example, theaforementioned water-soluble cellulose either (Metrose SM4000manufactured by Shin'etsu Kagaku Kogyo K. K.) the tackiness-inducedtemperature is 55° C. in the case of no additive, the tackiness-inducedtemperature is lowered to 40° C. when 5% by weight of sodium chloride(NaCl) or sodium carbonate (Na2CO3.10H2O) is added, hence, in the caseof direct application to the human body, Metrose SM4000 release theadsorbed water below the safety temperature (43° C.) for suppressing theexothermic reaction.

The tackiness-induced temperature of this Metrose SM4000 is 45° C. when5% by weight of Al2(SO4)3.18H2O is added, and at this temperatureMetrose SM4000 releases the adsorbed water around the metal powder tosuppress the exothermic reaction.

With 2% by weight of aqueous solution of, for example, water-solublecellulose ether (Metrose 60SH-4000 manufactured by Shin'etsu KagakuKogyo K.K.), the tackiness-induced temperature is 75° C. in the case ofno additive. The tackiness-induced temperature is lowered to 70° C. when5% by weight of sodium chloride (NaCl). The tackiness-inducedtemperature is lowered to 45° C. when 5% by weight of sodium carbonateNa2CO3.10H2O). At these temperatures Metrose 60SH-4000 releases theadsorbed water around the metal powder to suppress the exothermicreaction.

The tackiness-induced temperature of Metrose 60SH-4000 is lowered to 50°C. when 5% by weight of Al₂(SO₄)₃18H₂O is added and at this temperatureMetrose 60SH-4000 releases the adsorbed water for increasing thequantity of free moisture around the metal powder to suppress theexothermic reaction.

Examples for additives for adjusting the tackiness-induced temperatureof the aforementioned tackifiers include inorganic compounds andhydrates such as sodium chloride, sodium carbonate and aluminum sulfate,lower alcohols such as ethanol, polyhydric alcohols such as polyethyleneglycol and glycerin and also the aforementioned water-absorptive polymerand tackifiers.

The aforementioned poly-N-vinylacetoamide is obtainable by radicalpolymerization of N-vinylacetoamide and there are known two categories,one being of water-soluble direct chain structure and the other being ofwater-insoluble crosslinked structure. The water-insolublepoly-N-vinylacetoamide includes microgel which functions as gelatinizerbecause of the difference in crosslinking density, specificallyN-vinylacetoamide-sodium acrylate copolymer (GE-167 manufactured byShowa Denko K. K.), N-vinylacetoamide homopolymer (GE-191 manufacturedby Showa Denko K. K.) and N-vinylacetoamide crosslinked (microgel)(GX-205 manufactured by Showa Denko K. K.) used alone or in combinationof two or more. Further, these can be treated with some surfactant orcombined therewith for improved hydrophilic property. These tackifiershave a principal function of absorbing water or aqueous solution ofmetal halide for increasing consistency or imparting thixotropy.

For the invented composition organic matters are usable as an exothermicsubstance, but generally iron powder, zinc powder, aluminum powder ormagnesium powder or pulverized alloy of two or more of these metals freefrom generating odor but most preferred is iron powder with its safety,ease of handling, cost, storage property and stability.

As carbon components carbon black, graphite or active carbon are citedand as metal halides cited are chlorides of alkali metals such as sodiumchloride and potassium chloride and chlorides of alkaline earth metalssuch as calcium chloride and magnesium chloride.

The aforementioned inorganic or organic water retainers not only releasethe retained water when the water present in the exothermic compositionis insufficient and the exothermic reaction is slackened, but also byimproves the percentage of voids in the exothermic composition forimproving the chance of contract between air and the exothermiccomposition.

Specifically cited are such as pearlite, cristobalite, vermiculite,silicates such as calcium silicate, quartzite, silica-type poroussubstances silicates such as calcium silicate fluorite, diatomaceousearth, alumina, alumina silicate such as mica powder and clay, magnesiasilicate such as talc, silica powder, wooden flour and pulp powder.

As the aforementioned pH adjusters, surfactants and defoaming agents areused, besides ordinary pH adjusters such as sodium polyphosphate andmany others in common use in this field.

With the invented composition, it is advisable to have a part of thewater absorbed by the substrate and/or covering material to therebyimprove contact with the air when it is in use.

Since, as described above, the exothermic composition of the presentinvention is formed as a fluid, this allowing lamination thereof on asubstrate by, e.g., printing, it allows high-precision control of thelaminated region and thinness and form of the laminate, this allowinghigh-speed manufacture of the invented exothermic composition.

Since the invented composition is laminated on the upper surface of thesubstrate and after covering thereof with a covering material theexcessive moisture or free moisture or water in the water-containing gelis absorbed by the substrate and/or the covering material or thewater-absorptive layer, there is scarcely any progress of the exothermicreaction of the invented composition, hence loss due to exothermicreaction during manufacture, deterioration of the invented compositionor coagulation thereof can be precluded. Moreover, a part of water inthe invented composition is absorbed by the substrate and/or thecovering material and also the water-absorptive material, hence thedistribution of water in the invented composition at the time of use issuited for exothermic reaction, this resulting in good contact with airand possibility of accomplishment of the desired exothermic temperature.

Moreover, as described above, the invented composition with itsadhesiveness is laminated on the substrate by printing or coating and isadhered and fixed to the substrate as well as to the covering materialor the water-absorptive layer, thereby ensuring against movement of theinvented composition in the pouch, against scattering of the temperaturethereof and irregular displacement thereof in the pouch for preclusionof occurrence of any high-temperature region and against any risk oflow-temperature burn with increased safety in use.

Now the invented exothermic device will be described in detail.

The feature of the invented exothermic device is that the inventedcomposition is laminated and sealed in a thin pouch of sheet material atleast part thereof is gas-permeable.

The invented exothermic composition is as cited above and, moreover, itis so arranged that a part of water in the invented composition isabsorbed by the aforementioned thin pouch of sheet material.

In the invented exothermic device, the thin pouch of sheet material ismade up of a film of sheet substrate and film or sheet covering materialand it is desirable that at least either or a part thereof isgas-permeable and water-absorbable.

Although in the invented exothermic device the ultra-thin exothermicdevice is formed by printing, coating or the like, if the exothermicdevice is formed thin, decompression due to consumption of oxygen in airby the invented exothermic composition in the pouch is not sufficientfor further thinning (to less than 1 mm thick or so) and lightweightfeature, and forced attempt thereby results in lowering of per-hourexothermic reaction rate, this possibly interfering with maintenance ofthe degree of decomposition required to prevent movement and/ordisplacement in any direction of the invented exothermic composition.

In such a case it is preferable to prevent movement and/or irregulardisplacement thereof by fixing a whole or a part of the inventedexothermic composition to the substrate and/or the covering material.

Specifically, it is possible to form physical irregularity in thesurface of the substrate and/or the covering material at least in theregion supposed to be in contact with the invented composition or havethe substrate and/or the covering material formed of water-absorptivefilm or sheet and also have physical irregularity formed in the regionof contact with the invented composition so as to ensure againstmovement and/or irregular displacement of the invented composition dueto water-absorption-induced adhesion and irregularity-inducedresistance.

In the invented composition it is also preferable to have the substrateand/or the covering material of a non-gas-permeable or gas-permeablefilm or sheet laminated with a water-absorptive material on either orboth sides with a surface irregularity so as to ensure against movementand/or irregular displacement of the invented composition due towater-absorption-induced adhesion and irregularity-induced resistance.

That is, although it is desirable that the substrate and/or the coveringmaterial are formed of water-absorptive material, there is no limitationif the water-absorptive material is a water-absorptive film or sheet.

There is no particular limitation about the water-absorptive material aslong as it has a water-absorbency, regardless of water-absorbency of theraw material.

Specific examples are a foam film or sheet (e.g., water absorptivepolyurethane foam) and papers, nonwoven or woven fabrics made ofwater-absorptive fibers or nonwoven or woven fabrics includingwater-absorbing fiber, water-absorptive porous films or sheets, foamfilms or sheets, nonwoven and woven fabrics caused to incorporate orcarry a water-absorber by impregnation, kneading or transfer forimparting or enhancing water-absorbency or foam films or sheets, papers,nonwoven or woven fabrics or porous films or sheets regardless ofwater-absorbency stuck with water-absorptive foam films or sheets,papers, nonwoven or woven fabrics or porous films or sheets cut to theplanar size of the invented composition such that the inventedcomposition is in contact therewith.

In the invented exothermic composition it is desirable to have at leastpart of the substrate and/or the covering material in contact therewith.In this case, the water absorptive layer formed to be in contact withthe invented exothermic composition is desired to be easily stuck to thesubstrate and/or the covering material by sticking, heat-adhesion, orthermofusion along the periphery of the invented composition.

In the invented exothermic composition it is also desirable that thewhole or a part of the invented exothermic composition is buried in orbonded to the surface irregularity of the substrate and/or the coveringmaterial or the water-absorptive layer thereof for further ensuringagainst movement or irregular displacement thereof.

Thus, since movement of the invented exothermic composition in the pouchis prevented, irregular displacement and resultant scatter of orabnormal rise of the exothermic temperature can be prevented.

As the aforementioned water-absorptive material may be cited as theabove-mentioned water-absorptive polymer and/or a layer of tackifier ofthe above-mentioned film or sheet of water absorber.

The surface of the substrate and/or the covering material may possiblybe flat and smooth but is desirable to have a wetting index of at least38 dyne and preferably more than 40 dyne for secure bondage with theinvented exothermic composition. Hence, where the substrate and/or thecovering material has its surface formed of a smooth film or sheet, itis desirable to have its surface roughened by a physical treatment suchas corona treatment to thereby raise the wetting index.

When a water-absorptive layer is formed on the substrate and/or thecovering material where it comes into contact with the inventedexothermic composition, attraction of water into the exothermiccomposition results in migration into the substrate and/or the coveringmaterial and a part thereof to exhibit a powerful anchoring effect inthe water-absorptive layer, hence it is not particularly necessary toroughen its surface.

As mentioned above, the substrate and/or the covering material used inthe invented exothermic device has the invented exothermic compositiongenerating heat through contact with air as a heat source, hence it isnecessary that at least either or a part of the surface of the pouchformed by the substrate and the covering material is gas permeable, butthe substrate and/or the covering material is either single layer ormulti-layer in the direction of thickness.

In this case, lamination means alternatively overall or partiallayer-to-layer jointing by heat-setting, adhesion, gluing and laminationor simple piling of layers followed by heat-sealing or by the use of hotmelt adhesive or pressure sensitive adhesive along the periphery oraround the center.

In this case, the invented exothermic composition is fluid, hence theexothermic composition can be laminated by high-speed printing, coatingor the like and by laminating on the substrate by transfer, printing,gravure printing using a deep-engraved released plate, spray printing orcoating is feasible at a high speed of 160 to 200 m/minute or so with afilm thickness as small as 0.02 to 1.5 mm in at least one region andwith the laminate thickness kept uniform.

In this case, high precision and uniform lamination is made in at leastone predetermined region and, moreover, generally thin lamination isfeasible in a layer thickness of 0.02 to 1.5 mm or so and preferably 0.1to 0.5 mm or so, hence manufacture of an ultra-thin invented exothermicdevice generally 0.5 to 2 mm in overall thickness is obtainable.

In this case, for increased speed of processing, improved precision ofcontrol of the deposited region, thinning and uniformization, thesubstrate may be laminated with the invented exothermic composition withit being paid out from a roll film or roll sheet at a constant speed of,for example, 160 to 200 m/min., this followed by covering with acovering material also being played out from another roll film or rollsheet. In this case, the invented exothermic composition serves afunction similar to that of an adhesive for bonding the substrate withthe covering material, but it is advisable to have the periphery of theexothermic composition bonded or sealed.

The invented exothermic device is thus having the invented exothermiccomposition in at least one predetermined region in the upper surface ofthe thin substrate, this followed by placing the thin covering materialover this exothermic composition. In this case, too, the inventedexothermic composition plays a function similar to the tackifier. Ofcourse, for further improvement of quality as well as reliability, it isadvisable to seal the substrate and the covering material along theperiphery by sticking, heat-adhesion or thermofusion.

Where the substrate and/or the covering material is a single layer(single film or sheet), it is desirable, as mentioned above, to roughenits surface if it is smooth in surface or use foam film or sheet, paper,nonwoven or woven fabric or porous film or sheet. When such are ofwater-soluble material such as water-absorptive fiber, there is noproblem, but when the material has no water absorbency, the selectedproduct may be made water-absorbable by incorporating a water-absorptiveagent thereinto by soaking, impregnation, transfer or having it carriedinside. In this case, if foam film or sheet such as sponge, paper,nonwoven or woven fabric or the like is used, good adhesion with a layerof pressure sensitive adhesive will result as described below. When thesubstrate is a laminate of two or more films or sheets, see thedescription already given hereinbefore.

Where the invented exothermic composition is placed between thesubstrate and the covering material, it may be possible to have at leastone of iron powder, carbon component and water absorber (having a waterabsorptive ability) over the invented exothermic composition laminatedon the substrate for enhancing the rise of exothermic temperature in useor for helping control of temperature property. As to amenity controlthere has been no particular limitation in such cases; there is noparticular limitation as long as the temperature property is notaggravated, but generally it is advisable to have it in a range of 1 to250 g/m². As the water absorber, the aforementioned water-absorptivepolymer or tackifier may be used.

As to the invented exothermic device, it may as well be possible tolaminate an upper surface of the invented exothermic composition ironpowder coated with carbon component or mixture of iron powder (A) andcarbon component (B) and less than 5% by weight of water of the sum of(A) and (B) to thereby present flying of dust during lamination, enhancerise of the exothermic temperature in use and vary the temperatureproperty also in use.

In this case, iron powder is coated with a carbon component by the useof a pressing pressure type mixer, e.g., AM-15F manufactured by HosokawaMicron K. K., in such a manner that 0.1 to 10 parts by weight of carboncomponent is added to 100 parts by weight of iron powder and the mixeris operated at a rate of revolution of 500 to 1,500 rpm for 10 to 80minutes of kneading.

The method of obtaining a mixture of iron powder (A) and carboncomponent (B) and 5% by weight of the sum of (A) and (B) of water is bythe use of AM-15F manufactured by Hosokawa Micron K. K. and generallyunder conditions of 0.1 to 10 parts by weight of carbon component, 0.3to 5 parts by weight of water, particularly 0.5 to 3 parts by weight ofwater, per 100 parts by weight of iron powder, 500 to 1,500 rpm inrevolution and 10 to 80 min. in time of kneading. Addition of such aminute amount of water is effective for further prevention of flyingdust.

In the invented exothermic device the exothermic composition islaminated on the substrate and in the next step of covering the inventedexothermic composition a film or sheet-like water absorbing materialprecut in the lamination shape, especially thin paper for household usesuch as blotting paper and tissue paper and also highly water absorbingfilm or sheet precut in the lamination shape for the invented devicewere placed on one side of the invented exothermic composition or theinvented composition was sandwiched thereby before sealing with thecovering material.

In the present invention the method of incorporating a water absorberinto in film or sheet comprises having the film or sheet in a solutionof the water absorber and waiting for evaporation of the solvent orspraying the water absorber onto the film or sheet, this followed bycoating, kneading, pressing, lamination or compounding, interweavingwater-absorptive fibers into nonwoven or woven fabrics or blendingotherwise.

The aforementioned substrate and/or the covering material are requiredto have essential mechanical strength such as tensile strength and arepreferred to be generally soft and flexible to be well adaptable to thebody surface.

With the invented exothermic device, what is important includes improvedadaptability to the curved parts, stretching parts and bending parts ofthe human body and for further adaptability to the stretching parts andbending parts, the substrate and the covering material, i.e., the pouchof the exothermic device, are required to be extensile or, still better,stretchy film or sheet.

That is, the sheet forming the pouch is extensile or, still better,stretchy and is excelled in stretchability. Such exothermic devices arebetter suited for use on the bending parts, stretching parts and, stillbetter, expanding and contracting parts of the human body like joints inthe elbows and knees and, further, in shoulders and arms with retentionof excellent adhesion. Still better, there is no feeling of physicaldisorder or of being sticky in use and in addition to pleasant feelingin use, there is no risk of peeling off in use, being thus highlyfavorable for users especially with retention of excelled hot compresseffect.

As materials of such extensile substrate and covering materials may becited synthetic resins such as highly extensile polyethylene andpolypropylene.

As to extensile substrate and covering material, that is, extensilefilms or sheets there is no particular limitation as long as the rawmaterial used is extensile but there are many extensile foam films orsheets, nonwoven or woven fabrics and porous films or sheets wellcombinable with the invented exothermic device; regardless of thesehaving their own water absorptivity, wanted are those made waterabsorbable by having a water absorber contained therein or thereon orbeing carried thereby by such methods as impregnation, affixing,kneading, transfer and lamination, and desired is adoption of suchimproved materials for absorption of water in the invented exothermicdevice with simultaneous elimination of water barriers for restoring itsnatural porosity and the original good contact with air.

As raw materials for extensile films or sheets may be cited, forexample, natural rubber, synthetic rubber or thermoplastic elastomer.Being highly extensile, these are easy to handle and the thermoplasticelastomer is heat-fusible, thus these are supposed to largely facilitatemanufacture of this invented exothermic device.

Of course, the invented exothermic device has nothing to do with whetherthe substrate and the covering material have stickiness,heat-adhesiveness or thermofusibility, but for further improvement ofquality and reliability it is desirable to seal the substrate and thecovering material along the periphery of the exothermic composition bysticking, heat-adhesion, or thermofusion.

As the aforementioned synthetic rubbers may be specifically cited, forexample, butadiene rubber, isoprene rubber, styrene-butadiene rubber,acrylonitrile-butadiene rubber, chloroprene rubber, isobutylene-isoprenerubber, polyalkylene sulfide, silicone rubber, poly(chlorotri-fluoroethylene), flourinated vinylidene-6-flaunted propylenecopolymer, urethane rubber propylene oxide rubber, epichlorohydrinerubber, acrylic ester-acrylonitrile copolymer and acrylicester-2-chloroethylvinyl ether copolymer.

As the aforementioned thermoplastic elastomers may be specificallycited, for example, olefinic elastomer, polyurethane elastomer andpolyester elastomer.

As the aforementioned olefin elastomers may be cited, for example,ethylene-propylene copolymer, ethylene-propylene-diene terpolymer,chlorosulfonated polyethylene, chlorinated polkyethylene andethylene-vinyl acetate copolymer.

The thickness of the aforementioned substrate and the covering materialdepend largely on use, specifically being 10 to 5,000 μm with that for afoot and 10 to 500 μm, and more preferably 12 to 250 μm where it is useddirectly stuck to the human body, being thus generally in a range of 10to 2,500 μm and preferably in a range of 12 to 1,000 μm.

Where the film thickness of the substrate and the covering material isless than 10 μm, it is not preferable due to possible failure to obtainthe necessary mechanical properties and also due to possible difficultyto uniformize the film thickness.

Meanwhile, where the film thickness is in excess of 5,000 μm, theadaptability to the body surface is markedly lowered even in the case offoam such as sponge and the nature to follow variation or movement ofthe body surface is lowered and, worse, the feeling to the skin becomesrough or stiff and the thickness of the exothermic device as a wholebecomes too large, this being unfavorable.

Hence, it is preferable that the thickness of the substrate is in arange of 10 to 2,500 μm, and more preferably 12 to 1,000 μm.

As substrate and/or covering material, foamed or non-foamed films orsheets made of high-polymer materials may be cited but preferred arefilm or sheet foams, which anchors the invented exothermic compositionfor more secure prevention of its movement or irregular displacement.

As such high-polymer materials may be cited, for example, polyethylene,polypropylene, polyamide, polyvinyl chloride, polyvinylidene chloride,polyurethane, polystyrene, ethylene-vinyl acetate copolymer saponificateand ethyl-vinyl acetate copolymer.

Where the substrate or the covering material is of laminate type, partthereof may be made of gas-permeable film or sheet. As suchgas-permeable film or sheet are used foamed or non-foamed films orsheets, papers, nonwoven or woven fabrics, porous films and sheets,cloths or the like, and as cloths are usable woven, knitted or nonwovenfabrics and the like.

For imparting gas-permeability to a film or sheet made of theaforementioned non-foamed high-polymer materials there are known,besides the method of drawing the film or sheet in the course of itsmanufacture for formation of airholes or of forming airholes byextraction of specific components, a method of making airholes in theformed film mechanically by, e.g., punching or by the use of needles,and a porous film or sheet is thus obtainable.

Foamed films or sheets made of high-polymer materials have formedtherein independent or continuous air bubbles open to both, fore andback, surfaces and there are two alternatives, one pressing the formedfilm or sheet after foaming for rupture of the dependent or continuousair bubbles for communication to both sides and the other remainsgas-tight or not gas-permeable even after foaming.

Papers and cloths like woven, knitted and nonwoven fabrics havestructurally formed airholes communicating to both sides, thereby beinggas-permeable. As material fibers are usable natural fibers, regeneratedfibers made of natural materials such as viscose fiber, semisyntheticfibers and synthetic fibers as well as mixtures of two or more thereof.

As natural fibers are known vegetable fibers such as cotton and linenand animal fibers such as silk and animal hairs. As high-polymermaterials constituting synthetic fibers are known, among others,polyethylene, polypropylene, polyamide, polyester, polyvinyl chloride,polyvinylidene chloride, polyurethane, polystyrene, ethylene-vinylacetate copolymer saponificate and ethylene-vinyl acetate copolymer.

The invented exothermic device is required to have at least one of or apart of the sides or the substrate and the covering material forming itspouch to be gas-permeable.

Where at least either or a part of the substrate and the coveringmaterial is gas-permeable, the gas-permeability largely influences thecontrol of the reaction rate or exothermic temperature of the exothermiccomposition, hence proper control of gas-permeability is preferable forobtaining proper exothermic effect and for ensuring safety throughprevention of low-temperature burn. For high-precision control of thisgas-permeability, it is preferable to control the gas-permeability offilm or sheet by means of water-vapor permeability. Specifically, thewater-vapor permeability is to be controlled in a range of 50 to 10,000g/m²24 hr and preferably in a range of 200 to 6,000/m²24 hr according tothe Lyssy method L80-4000H type.

Where the substrate and/or the covering material is composed of aplurality of gas-permeable films, it is preferable to control the totalwater-vapor permeability in a range of 50 to 10,000 g/m²24 hr alsoaccording to the Lyssy method.

When this water-vapor permeability is less than 50 g/m²24 hr nosufficient exothermic effect is attainable, while, if it exceeds 10,000g/m²24 hr, the exothermic temperature becomes too high, thereby givingrise to safety problems, or the exothermic time is likely to be tooshort. Hence, it is particularly preferable to have the water-steampermeability of the gas-permeable film controlled in the range of 100 to1,000 g/m²24 hr whereby safety is ensured and sufficient exothermiceffect can be retained over a long time.

A Lyssy method is a method in conformity to the industrial standards inmany countries of the world and in JIS Z020 to Z0208 it is determined tokeep the relative humidity difference at of 100% RH at the ambienttemperature of 40° C. Hence in this apparatus the sample for measurementis inserted between the lower chamber 90% RH and the upper chamberhaving therein a highly sensitive humidity sensor. The relative humidityin the upper chamber is kept at 10% RH (100%-90%) and with this as thecenter the time (several seconds) required for rise of humidity fromapproximately 9% to approximately 11%=approximately±1% (RH) and thehumidity permeability is determined by comparison with the result ofcalibration carried out in advance under the same conditions using thestandard sample of known permeability.

In the invented exothermic device, at least part of the exposed surfaceof at least either of the substrate and the covering material has formedthereon an adhesive layer at any time before inclusion in the gas-tightouter bag. In this case, the other gas-permeable side is preferable forit is then directly applicable to the body surface or fixable to be usedwith clothes.

As to this adhesive layer, there is no particular limitation as long asit is adherable to a skin surface, but specifically cited, for example,a layer comprising a wet compress agent or an adhesive.

As the aforementioned adhesive layer, layers may be prepared by the useof solvent-type adhesive, emulsion-type adhesive or hot-melt typeadhesive.

As preferred adhesive layers, layers specifically containing, forexample, rubbery adhesive agents, vinyl acetate adhesive agents,ethylene-vinyl acetate adhesive agents, polyvinyl alcohol adhesiveagents, polyvinyl acetal adhesive agents, vinyl chloride adhesiveagents, acrylic adhesive agents, polyamide adhesive agents, polyethyleneadhesive agents, cellulose adhesive agents, polysulfide adhesive agentsand hot-melt type high-polymer-containing adhesives but, of these,preferred are the layers containing rubbers adhesives, acrylic adhesivesand hot-melt type high-polymer-containing adhesive agents proper fordirect sticking to the skin, being less stimulative to the skin and lessdrop in adhesiveness even if a hot compress agent is added andparticularly preferred is the adhesive layer containing thehot-melt-type high-polymer substance for its excelled initial tackingforce and extremely good adhesiveness at the warming temperature.

There is no particular limitation for the thickness of such adhesivelayers but normally in a range of 5 to 1000 μm, preferably 10 to 500 μmand more preferably 15 to 250 μm. If the thickness of the adhesive layeris less than 5 μm, the required adhesive force may possibly be difficultto obtain, while, if it is in excess of 1000 μm, bulky feel becomesdisagreeable and less preferable also for cost reasons.

As hot-melt type high-polymer substances usable for the inventedexothermic devices are specifically, for example, A-B-A type blockcopolymers, saturated polyester-type high-polymer substances,polyamide-type high-polymer substances, acrylic-type high-polymersubstances, urethane-type high-polymer substances, polyolefin-typehigh-polymer substances and polyolefin-type copolymers, denaturedsubstances thereof and mixtures of two or more thereof.

The aforementioned denatured substance is one having a part ofingredients of a hot melt-type high-polymer substance substituted byother ingredients for, for example, improvement of adhesiveness ormodification of stability etc. of the hot melt-type high-polymersubstance.

In the aforementioned A-B-A type block copolymers the “A” blockrepresents monovinyl-substituted aromatic compounds such as styrene andmethyl styrene, being thus a block non-elastic polymers, and “B” blockrepresents a block of elastic polymers or conjugate dienes such asbutadiene and isoprene, specifically, for example, styrene butadienestyrene block copolymer and styrene-isoprene-styrene block copolymer,and these may possibly be mixed properly.

As examples of commercially available products of the A-B-A type blockcopolymers are given, Cariflex TR-1101, Cariflex TR-1107, CariflexTR-1107, Cariflex TR-1111 manufactured by Shell Inc.) and Solprene 418manufactured by Phillips Petroleum Inc.

If desired, such adhesives may be admixed with proper amounts of othercomponents such as other adhesives, adhesiveness-imparting agents,anti-aging agents, fillers, adhesion adjusters, adhesion improvingagents, colorants, defoamers, tackifiers, modifiers, mildewproofingagents antibacterial agents, insecticides and/or deodorants.

Such adhesive layer may be formed on the exposed surface of either ofthe substrate or the covering material by direct application. In orderto make sure that the adhesive layer is secured on the exposed surface,it is preferable to roughen the exposed surface of the substrate or thecovering material or to form the substrate or the covering material outof paper, woven fabric, knitted fabric, nonwoven fabric or foamed filmso that the exposed surface becomes rough.

In the invented exothermic device it is preferred if the exposed surfaceof the substrate and/or the covering material is covered with a wetcompress layer or a medication layer containing therein or carriedthereby skin-absorbable medicines for this enables wet compress effectand medication effect in addition to hot compress effect. With theaforementioned skin-absorbable medicines there are no particularlimitations as long as long as the medicines used are skin-absorbablebut the medicines may include, specifically, skin-stimulant,anodyne/antiphlogistic agent, central nerve active agent(soporific/sedative, psychoneurotic agent, etc.), diuretic, hypotensive,coronary vasodilator, expectorant, antihistaminic, anti-arrhythmic,cardiac, adrenocortical hormone drug, and local anesthetic. One type ofthese medicines, or two or more types thereof may be used.

The amount of medication used is not limited as long as a medical effectis expected, but may be determined from the point of view ofpharmacological effect and economy, the content of skin absorbablemedicines is properly determined in a range of 0.01 to 25 parts byweight, and preferably 0.5 to 15 parts by weight, in relation to 100parts by weight of the adhesive.

With the invented exothermic device, it is desirable to have ceramicpowder or molding thereof radiating far infrared rays placed in theexothermic composition and/or in the adhesive layer side of theexothermic device for accomplishing the effect of far infrared rays.

The ceramic material radiating far infrared rays may be used togetherwith or in place of the exothermic composition. This ceramic materialmay be enclosed in the pouch along with the exothermic composition, ormay be carried by a carrier as is the exothermic composition. Further,the ceramic material may be carried by the adhesive layer.

In this case, the heating effect promotes blood circulation. When usedwith the skin absorbable medication, the ceramic material increases theskin absorptivity of the medication to enhance the general or localtherapeutic effect.

The exothermic device thus obtained not only supplies warmth to thehuman body in water to help people enjoy pleasant life indoors, but alsois sufficiently effective therapeutically as a warm compress means, andnow they are being used widely to help cure local stiffness, symptomsaccompanying pain and chill, for example, stiffness in the shoulder,stiffness in muscles, lumbago, chill in hands and feet, neuralgia,rheumatism, bruises, sprains and other diseases and disorders.

In the exothermic device according to the present invention, thesubstrate and/or the covering material are formed of film or sheet foam,nonwoven or woven fabric or porous film or sheet on one side or on bothsides of a non-air permeable or gas-permeable film or sheet, this beingdesirable for it ensures against movement or irregular displacement ofthe exothermic composition when a fluid exothermic composition islaminated on one side, and it is particularly desirable when the otherside is covered with a nonwoven fabric or woven fabric for the feel orhandling is markedly improved thereby.

In the invented exothermic device the invented composition formed as afluid is used as laminating material and lamination is done by printingor coating, this allowing uniform and ultra-thin lamination, hence theexothermic device is ultra-thin and extremely soft and flexible, beingvery well adaptable to curved or bent parts of such as a shoulder andbeing also excelled in feel in use.

Since in the manufacture of the invented exothermic device the inventedcomposition is used in a fluid form, the excessive moisture, freemoisture or water-containing gel is used for barrier formation, thisresulting in markedly slower progress of exothermic reaction involvingthe invented composition in the course of manufacture. While the loss ofthe invented composition due to exothermic reaction as a step ofmanufacture and deterioration of the quality of the exothermiccomposition or coagulation thereof is prevented, the water contained inthe exothermic composition is absorbed into the pouch before use, thewater content of the exothermic composition is suited for the exothermicreaction at the time of use, this resulting in marked improvement of theproduct such as the possibility of the exothermic temperature reachingthe desired level at the time of use, and this, in turn, results inremarkably high quality and reliability of the product.

Moreover, in the invented exothermic device movement inside the pouch ofthe invented composition can be prevented, scattering of temperature orirregular displacement of the exothermic composition and partialgathering and resultant formation of high-temperature spots can also beprevented without fail, this ensuring against the risk oflow-temperature burn, and the safety of this product is markedly raised.

Especially, since in the invented exothermic device the inventedexothermic composition comes into direct contact at spots havingwater-absorbing property, the exothermic composition is attracted by thesubstrate and/or the covering material or the water-absorptive layerwith absorption of excessive moisture in the invented composition orfree moisture or water from the water-containing gel, this followed by aportion of the invented composition migrating into the substrate and/orthe covering material or the water-absorbing member to give rise to theso-called anchoring effect which secures the invented exothermiccomposition in the substrate and/or the covering material or thewater-absorptive member or the water-absorptive layer.

In this case, if the contact spots among the substrate and/or thecovering material and the invented exothermic composition are formed ofwater-absorbable foam film or sheet, nonwoven or woven fabric or porousfilm or sheet, bondage with the invented composition is further improvedand movement and irregular displacement of the invented exothermiccomposition is prevented more securely as well as various harms causedby irregular distribution of the invented exothermic composition.

Where in the invented exothermic device the substrate and/or thecovering material or the water-absorptive layer is/are water absorbent,a part of the water in the invented exothermic composition is absorbedbefore use, this allowing adjustment of the water content of theinvented exothermic composition to a level suited for exothermicreaction. If this is done, it is possible to have the exothermicreaction readily started with breaking of the gas-tight bag and thepredetermined exothermic temperature is attained quickly and as theexothermic reaction proceeds, the water vaporized from the exothermiccomposition is replenished with water discharged from the substrateand/or the covering material, this allowing maintenance of the requiredexothermic temperature over a long period of time.

In the invented exothermic device, if either or both sides of theinvented exothermic composition is/are covered with a thin film or sheetof water-absorptive material especially paper or high water-absorbency,a portion of the water retained in the invented exothermic compositionis absorbed and the exothermic composition is securely fixed to thewater absorptive material.

In the invented exothermic device, if the adhesive layer at least one offar infrared ray radiator, magnetizer or skin absorption medication iscontained therein or carried thereby, far infrared ray heating effect,far infrared ray therapeutic effect, magnetic therapeutic effect andmedication-induced therapeutic effect can naturally be expected but sucheffects may be further enhanced synergistically such general or localeffect as the enhanced blood circulation by the warmth generated byexothermic reaction.

Next, the first method of the invention will be described in detail.

In the first method of the invention what is performed first is the step(A) for manufacture of an exothermic composition, i.e., the inventedcomposition is formed as a fluid. The invented substance used here isthe same as that described above.

For manufacturing the invented substance there are two alternativemethods of

-   -   throwing all of the aforementioned components in a mixer, this        is followed by uniform mixing, or of    -   throwing in all solid components of the aforementioned        components, uniformly mixing these components in the mixer, then        adding water and the resulting aqueous solution of metal halide        or dispersion before mixing are useful for obtaining the        aforementioned exothermic component. As to the mixer, there is        no particular limitation as long as the components of the        invented composition are uniformly mixable but also usable are,        specifically, ribbon mixer, spallation mixer, screw blender,        roll mixer, Banburry mixer and kneader.

Where in the manufacture of the invented composition water content isexcessive, for example, when it is fluid, any kind of mixer may be used.Meanwhile, when the exothermic composition is fluid, the proportion ofwater is relatively small, hence the use of an apparatus such as a mixeror a kneader for kneading components under pressure is easy for makingthe exothermic composition fluid and, moreover, the squeezed-out waterbecomes free of moisture and after manufacture of the fluid exothermiccomposition the free moisture is absorbed by the gel in the periphery ofthe exothermic composition, hence this free moisture or water-containinggel as a barrier layer against contact with air, being thus effectivefor stabilization of the exothermic composition.

In the present invention the invented substance obtained in the step (A)is then transferred to and laminated in at least a given region in theupper surface of a thin substrate in the next step (B).

The substrate used here is the same as what was described in relation tothe invented exothermic device, hence description thereof is omitted foravoiding repetition.

In the step (B) of the invented composition, the invented composition istransferred or laminated in a given shape on the upper surface of thesubstrate by printing or coating but the invented composition maypossibly be laminated at one or two or more spots sidewise on the uppersurface of the substrate or zigzag longitudinally.

In the present invention the invented composition is covered with a thincovering material in the step (C).

The covering material used here is the same as what was described inrelation to the invented exothermic device, hence description thereof isomitted for avoiding repetition.

Here the substrate and the covering material are stuck together with theinvented composition in between. Since the invented composition plays arole similar to that of an adhesive, it is not essential to have thecomposition and the covering material sealed along the periphery of theinvented composition, but it is desirable to have this sealing along theperiphery of the invented composition by sticking, heat-adhesion orthermofusion for further improvement of the product's quality as well asits reliability.

Since the first method of the present invention is for manufacturing theinvented exothermic device which generates heat through contact withair, at least either or a part of the aforementioned substrate and thecovering material is required to be gas-permeable.

In the method of the present invention a thin sheet of water-absorptivematerial may be applied to either or both sides of the inventedcomposition to have a part of the water present in the inventedcomposition absorbed thereby. Specific examples of this water-absorptivematerial are cited above.

In the first method of the present invention the invented composition isa fluid consistency, this giving rise to the various merits describedbelow.

In the first method of the present invention lamination by printing suchas screen printing or coating is extremely easy when an exothermiccomposition is fluid, i.e., the invented composition, is used, andultra-thin exothermic devices are manufacturable at a high speed.Moreover, the method allows uniform distribution of the exothermiccomposition in the pouch and, further, when the invented composition isplaced or sandwiched between the substrate and the covering material offoam film or sheet, papers, nonwoven or woven fabric or porous film orsheet, the invented composition with its high penetrating and anchoringeffect gets into pores of such substrate and covering material and thusmovement or irregular displacement thereof in the pouch is prevented.

In this case, especially when the composition and/or the coveringmaterial is/are water-absorptive and the invented composition islaminated on the substrate or a water-absorptive layer is firstlaminated and the invented composition is laminated thereon, this isfollowed by coverage with the aforementioned covering material, whole ora portion of the exothermic composition is fixed to the water-absorptivesubstrate and/or the covering material or water-absorptive layer formedthereon and its movement or irregular displacement is prevented moresecurely.

Lamination by printing or coating enables extreme thinning of thisexothermic device and the resulting thin exothermic device with itsper-hour progress of exothermic reaction is effective for excessiveexothermic reaction of the exothermic composition and has such otherfeatures as being soft and flexible, being better adaptable to expansionand shrinkage of the outer cover and being improved in feel in use.

Further, in the first method of the present invention, if the adhesiveaqueous solution of the water-absorptive agent is contained in ordeposited on the sheet forming the pouch such as foam film or sheet,paper, nonwoven or woven fabric or porous film sheet by impregnation,spraying or kneading, or the thin pouch first made water-absorptive andthen laminated with the invented composition by screen printing orcoating, this followed by drying, the step of throwing-in dust can beeliminated and plant control well meeting GMP supposed to be applied inthe near future to the manufacture of medical instruments and medicines.As a water-absorptive agent used here, the aforementionedwater-absorptive polymer or tackifier may be cited.

Thus, the first method of the present invention has such various meritsas mentioned above since the invented composition is a fluid but thisinvented composition is very well suited for transfer or lamination byprinting or coating, this allowing high-speed manufacture of extremelythin exothermic devices, and is remarkably small in specific surfacearea compared with powdery exothermic compositions and the resultantdecrease of air supply causes substantial stopping of the exothermicreaction to thereby enabling elimination of loss due to exothermicreaction in the course of manufacture and prevention of lowering of thequality of exothermic composition and coagulation thereof.

If, in the first method of the present invention, the excessivemoisture, free moisture and a portion of the water. In thewater-containing gel is absorbed by the pouch material such as thesubstrate and/or the covering material, loss of the water barrier andthe resulting enhancement of contact with air of the now porousexothermic composition cause improvement of the temperature properly inuse.

In the first method of the present invention, this exothermiccomposition can be laminated on the substrate by transfer or byprinting, this enabling high-precision control of the laminating regionand formation of extremely thin and uniform layer of exothermiccomposition film, the result being the possibility of high-speedmanufacture of ultra-thin sheet of the invented exothermic composition.

In the first method of the present invention, the water content of theinvented composition is raised to such an extent that its solution isfluid as it is laminated on the substrate. Since, however, water isabsorbed by the substrate and/or the covering material or thewater-absorptive layer, the exothermic reaction of the inventedcomposition is scarcely noticeable at the time of manufacture, hence theloss due to exothermic reaction in the course of manufacture can beprevented as well as lowering of quality of the exothermic compositionand coagulation thereof and, furthermore, a portion of the water contentof the invented composition is absorbed by the substrate and/or thecovering material or the water-absorptive layer so that the watercontent becomes proper for the exothermic reaction by the time of use,this resulting in increased reliability of the invented exothermicdevice.

In the first method of the present invention, the invented compositionused is a fluid and can be accurately laminated in the predeterminedregion on the substrate without undue loss, this enabling manufacture ofthe invented exothermic device for effectively warming any specificregion, hence an excellent warming effect and blood-circulationpromoting effect are effectively obtainable. Another remarkable featureis that there is no risk of dust diffusion in the process ofmanufacture, hence plant control perfectly meeting the GMP standardsapplicable in the near future to the manufacture of medical appliancesand medicines.

In the first method of the present invention, the process of laminatingthe fluid exothermic composition, covering the same with the coveringmaterial and packing the made exothermic devices is feasible integrallyand in a very short period of time, hence there is no risk of theexothermic composition being subjected to conditions possibly triggeringexothermic reaction and there is no likelihood of the inventedcomposition generating heat in the course of manufacture.

As the result, lowering of the quality of the invented composition orcoagulation thereof in the course of manufacture can be completelyprecluded, known harms such as lowering of yield, handling difficulty,complexity of machine maintenance, limitation of machine's operatinghours and worker's working hours and the difficulty of disposal ofcoagulated compositions can be all eliminated and the high-quality andhighly reliable exothermic devices can thus be obtainable at a stilllower cost.

Then the second method of the present invention will be described indetail.

According to the second method of the present invention, the inventedcomposition is first produced and after laminating the same in at leastone predetermined region on the upper surface of the thin substrate atleast one of iron powder, carbon component and water-absorptive agent islaminated or sprayed and the thin covering material is placed to coverthe selected one of iron powder, carbon component and water-absorptiveagent, featuring that either or a part of the aforementioned substrateand the covering material is gas-permeable.

According to the second method of the present invention, a film or sheetof water-absorptive material may be applied to either or both surfacesof the invented composition for a part of the water in the inventedcomposition to be absorbed thereby. Specific examples of thiswater-absorptive material are cited above. In this case, either or bothsides of the invented composition is/are meant side/s of the inventedcomposition laminated by of sprayed with at least one selected from ironpowder, carbon component or water-absorptive agent.

Hence, the covering material is placed to cover at least one selectedfrom the invented composition, iron powder, carbon component andwater-absorptive agent.

According to the second method of the present invention, the inventedexothermic device is of the type generating heat through contact withair, hence at least part of the pouch formed of the aforementionedsubstrate and/or the covering material is gas-permeable. The substrateand the covering material are the same as those explained in relation tothe invented device, hence explanation about these will be omitted foravoiding repetition.

The second method of the present invention is different from the firstmethod of the present invention only in that at least one selected fromiron powder, carbon component and water-absorptive agent is laminated orsprayed on the upper surface of the invented composition and then placea thin covering material to cover the selected one of iron powder,carbon component and water-absorptive agent, being the same as the firstmethod of the present invention, hence explanation thereof will beomitted for avoiding repetition.

According to the second method of the present invention, the inventedcomposition, i.e., the exothermic composition made fluid by increasingthe water ratio to a level required therefor, is formed, this inventedcomposition is laminated in at least one of the predetermined regions onthe upper surface of the thin substrate, then the laminated uppersurface is laminated or scattered with at least one selected from ironpowder, carbon component and water-absorptive agent, this followed byplacing a film or sheet of covering material to cover the same, andthereafter using the invented composition to cause the substrate and thecovering material to be bonded together and, moreover, it is so arrangedthat a portion of the water present in the invented composition isabsorbed by the substrate or the covering material or the waterabsorptive agent, featuring high-precision control or the region to belaminated, extremely small film thickness attainable, the possibility oflaminating the surface of the substrate uniformly with the inventedcomposition, the possibility of producing an extremely thin layer of theinvented composition at a high rate and, further, the possibility ofimproving the initial rise of temperature or temperature property byinter-layer lamination or scattering of iron powder. Also, according tothe second method of the present invention, the exothermic substancepresent in the invented composition is covered by the excessivemoisture, free moisture or water-containing gel, the contact with oxygenof air is suppressed by the presence of excessive moisture to therebyprevent exothermic reaction of the exothermic substance, this resultingin preclusion of loss due to exothermic reaction and prevention oflowering of the quality of the invented composition and coagulationthereof in the course of manufacture. After completion of manufacture ofthe invented composition, the aforementioned water present in theinvented composition is absorbed by the water-absorptive agent laminatedor scattered, the substrate and also the covering material, thisresulting in that the water content of the exothermic composition in theexothermic device will be optimum for an exothermic reaction by the timeit reaches an end user.

Since, according to the second method of the present invention, theprocess of laminating a fluid exothermic substance on the substrate andof placing the covering material to cover the same and subsequent stepof packing the completed exothermic devices can be made integral and thetime required is extremely short, hence there is little chance foroccurrence of conditions in the manufacturing process causing anexothermic composition to generate heat and heat generation of theinvented composition in the manufacturing process is thus precludable.

As a result, lowering of the quality of the invented composition orcoagulation thereof in the course of manufacture can be completelyprecluded, known harms such as lowering of yield, handling difficulty,complexity of machine maintenance, limitation of machine's operatinghours and worker's working hours and the difficulty of disposal ofcoagulated substances can be all eliminated and the high-quality andhighly reliable exothermic devices can thus be obtainable at a stilllower cost.

Next, the third method of the present invention will be described indetail.

According to the third method of the present invention, first theinvented exothermic composition is laminated on a thin substrate, then afilm or sheet of covering material is placed to cover the same and theaforementioned substrate and covering material are stuck together by theviscosity of the invented composition for completion of a laminate.

In this case, a sheet or film of water-absorptive layer may possibly beapplied to either or both sides of the invented composition.

According to the third method of the present invention, the inventedcomposition used is the same as described above, hence explanation aboutit will be omitted for avoiding repetition.

According to the third method of the present invention, too, since theoxidation reaction, i.e., exothermic reaction is suppressed even if theinvented composition comes into contact with air until a part of thewater present in the invented composition is absorbed by thewater-absorptive substrate and/or the covering material. Hence loss ofthe exothermic composition due to the exothermic reaction duringmanufacture, lowering of the quality of the exothermic composition andcoagulation thereof can be almost surely prevented. Moreover, theinvented composition is a fluid, this permits lamination in a uniformthickness. Further, the invented composition is viscous, being alsoadhesive to the pouch, hence movement or irregular displacement of theexothermic composition can be prevented and excessive exothermicreaction of the exothermic composition is precludable.

According to the third method of the present invention, there is noparticular limitation with regard to the method for laminating theinvented composition on the substrate but specifically cited are, amongothers, coating by the use of a coater such as head coater, roller,applicator and the like.

Since the third method of the present invention is for obtaining theinvented exothermic device generating heat through contact with air,either the aforementioned substrate or the covering material or at leasta part thereof is gas-permeable. Since the substrate and the coveringmaterial are the same as those described in relation to the inventedexothermic device already described, hence explanation about these willbe omitted for avoiding repetition.

According to the third method of the present invention, the exothermicdevice is obtainable by stamping out the resulting laminate in apredetermined shape. Hence, the substrate and the covering material arerequired to be easy to stamp out and from this viewpoint it is desirableto use paper or the like as material of the substrate and the coveringmaterial.

The aforementioned step of stamping-out pieces of predetermined shapefrom the aforementioned laminate may also be done with the laminate keptstationary and, should it be the case, a large number of exothermicdevices can be made at once by doing stamping-out simultaneously with aplurality of laminates fixed along the feeding direction and also alongthe sidewise direction at proper intervals, this being effective alsofor cost reason.

This method is, however, problematic as follows. When, as mentionedabove, the invented composition is laminated on a thin substrate beingplayed out of a roll film or roll sheet at a speed of 160 to 200 m/min,and then a thin covering material being played out of another roll filmor roll sheet is placed thereon for continuous formation of a laminate,stopping the laminate in the stamping-out process means the necessity ofwinding back the formed laminate once and then playing outintermittently. This complicates the manufacturing process withprolongation of the required time and, worse, intermittent stamping-outoperation interferes with the desired improvement of the workingefficiency.

According to the third method of the present invention, it is preferableto obtain the invented exothermic devices using a roll press forstamping-out in any arbitrary shape with the laminate being fed at thefeeding speed in the manufacturing process therefor, for example, 160 to200 m/min.

When a roll press is used, continuous stamping-out of laminate isfeasible and, moreover, manufacture of the laminate and stamping-out canbe integrated to enable continuous operation, hence a large number ofexothermic devices can be manufactured with the cost much less than inthe method of stamping-out the laminate intermittently.

The above method is further improved in working efficiency as well as incost reduction when stamping is done at two or more spots sideways withthe substrate or the like being fed continuously and especially whenlongitudinal stamping-out is done in a zigzag fashion, this resulting ina much more saving of the cost.

The stamping-out shape may arbitrary according to the intended use forthe obtained exothermic device.

According to the third method of the present invention, the obtainedlaminate is stamped in any desired shape but the stamped-out pieces ofthe invented exothermic device are not particularly limited for use suchas for a foot, shoulder and waist.

According to the third method of the present invention, the substrateand the covering material are stuck together by the viscosity of theinvented composition but thereafter a part of the water is absorbed bythe substrate and the covering material and the exothermic devices thusobtained are commercially valid for they are distributed after sealingin non-gas-permeable outer bags.

However, it is desirable to interpose the stamped-out piece of theinvented device between two other layers of film or sheet, to have thetwo layers of film or sheet stamped into a size greater than thestamped-out piece of the invented exothermic device at the time of orafter the insertion thereof and then to seal together the two layers offilm or sheet along the periphery of the aforementioned inventedexothermic device at the time of or after the stamping-out operation.

Here, at least either or a part of the aforementioned two layers of filmor sheet is gas-permeable and thus the obtained invented exothermicdevice is further improved in reliability.

That is, an invented exothermic device of an arbitrary shape is obtainedin this process but the volume of air supplied to the exothermiccomposition inside thereof is controlled by the gas-permeability ofthese two layers of film. Hence the gas-permeability or suppliability tothe invented composition is controlled on the basis ofmoisture-permeability like that of the substrate and/or the coveringmaterial. The humidity-permeability of either of the two layers of filmor sheet or of laminate of film/sheet as substrate and covering materialis the same as in the case of the invented composition and the inventedexothermic device, hence explanation about it will be omitted foravoiding repetition.

The aforementioned two layers of film or sheet are either gas-permeableor non-gas-permeable and these may possibly be adhesive, hot-meltbondable or heat-sealable.

The aforementioned adhesive film or sheet includes a base film or sheetand a gas-permeable adhesive layer formed thereon. Such an adhesivelayer is made entirely of a gas-permeable hot-melt adhesive or is madeof part of a gas-permeable adhesive and part of a non-gas-permeableadhesive. The base film or the base sheet itself may not be necessarilyheat-melt bondable or heat-sealable.

According to the third method of the present invention, if the lengthyexothermic composition is already made, two layers of film or sheet maybe sealed together along the periphery of the individual exothermicdevices before, during or after stamping.

Stamping-out pieces of film or sheet are required to be greater in sizethan that of the particular exothermic device and also required to besimilar or substantially similar in shape thereto and it is desirable ifthe size of the former is greater by several mm to 20 mm along theentire periphery (extended edge).

According to the third method of the present invention, theaforementioned tow layers of film or sheet are to be sealed together inthe extended edge or along the entire periphery of the exothermic deviceby sticking, heat-adhesion, or thermofusion.

According to the first to the third method of the present invention,either side of the invented exothermic device is desired to have thewhole of a part of the exposed area covered with an adhesive layer andat least part of the opposite side is desired to be gas-permeable.

The adhesive layer may possibly be a wet compress layer containing a wetcompress agent or a medication layer containing or carrying skinabsorbable drug/s, but since this is the same as in the case of theinvented exothermic device, explanation about it will be omitted foravoiding repetition.

The adhesive layer may have contained therein or carried thereby atleast one of far infrared ray radiators or magnetic means.

According to the first to the third method of the present invention, apart of the water present in the invented composition is absorbed by thesubstrate and/or the covering material or by the water-absorptivematerial applied to either or both sides of the invented compositionfrom the time of its manufacture by the time it is actually used, andthe free moisture or a part of the water present in the water-containinggel is absorbed by the substrate and/or the covering material or thewater-absorptive material applied to either or both sides of theinvented composition. This results in a formation of a porous exothermiccomposition which makes good contact with air and readily causes anexothermic reaction upon contact with air.

According to the third method of the present invention, the inventedcomposition, namely a fluid exothermic composition, is laminated on thefilm substrate and the thin covering material is placed to have itenclosed thereby, the aforementioned substrate and the covering materialare stuck together by the viscosity of the invented composition, thenthe resulting laminate is stamped for formation of pieces of any desiredform and at least either or part of the aforementioned substrate or thecovering material is gas-permeable.

Hence, an extremely thin exothermic device is manufacturable and,moreover, the invented composition, i.e. a fluid exothermic composition,is used, hence the exothermic reaction is controllable through barrierformation by excessive moisture or the like, this possibly causingelimination of loss due to exothermic reaction in the course ofmanufacture, and preclusion of various harms caused by prevention oflowering of the quality of the invented composition and coagulationthereof and, furthermore, uniform distribution of the inventedcomposition in a pouch or causing it to be fixed thereto enablespreclusion of movement or irregular distribution of the exothermiccomposition, this enabling preclusion of excessive exothermic reactionof the exothermic composition for prevention of low-temperature burnand, further, allowing manufacture of the invented exothermic devicequite safe to use.

According to the first to the third method of the present invention,application of a thin sheet of water-absorptive material, especiallyhighly water-absorbable paper to either or both surfaces of the inventedcomposition, a part of the water present in the invented composition canbe absorbed by the paper and, furthermore, secure fixing of such paperto the invented composition is caused thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an exothermic device in a firstembodiment of the present invention;

FIG. 2 is a schematic sectional view of an exothermic device in a secondembodiment of the present invention;

FIG. 3 is a schematic sectional view of an exothermic device in a thirdembodiment of the present invention;

FIG. 4 is a schematic view of an exothermic device in a forth embodimentof the present invention;

FIG. 5 is a sectional view showing essential parts of the exothermicdevice of the fourth embodiment of the present invention; and

FIG. 6 is an explanatory view showing the test method used forinvestigating the stability of the exothermic composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will particularly be describedhereinafter with reference to the drawings. It should be understood,however, that the present invention is not limited to these embodiments.

An invented exothermic device referred to in a first embodiment of thepresent invention has, as shown in the schematic sectional view of FIG.1, a fluid exothermic composition, i.e., the invented composition 2,sealed in a flat and rectangular pouch 130 mm long and 95 mm wide, theaforementioned pouch 1 is, in this case, made of a non-gas-permeablesubstrate 3 and a gas-permeable covering material 4 and, moreover, anadhesive layer 5 to 100 μm thick is formed on the exposed surface of thesubstrate 3.

The substrate 3 is made of a non-gas-permeable polyethylene film 3 b 40μm thick for being sufficiently soft and flexible and having formed onone surface thereof a water-absorptive polymer-containing polyesternonwoven fabric (Sanwet IM-5000MPS 10 g/m² and 210 μm thick) 3 a and onthe other surface a nonwoven fabric made of rayon/polyester blendcontaining 60% by weight of rayon (140 μm thick) 3 c.

The covering material 4, which is required to be high in mechanicalstrength and also required to be sufficiently soft and flexible, may,for example, be made of porous polyethylene film 4 a having a thicknessof about 100 μm laminated on one side with nylon nonwoven fabric 4 b 150μm thick.

This covering material 4 has its humidity-permeability (humid permeablevolume as measured by the Lyssy method) adjusted to be 400 g/m²24 hr.

Further, the adhesive layer 5 is for adhesion of the pouch to the outerbag, and this adhesive layer 5 is formed of an adhesive ofstyrene-isoprene-styrene block copolymer type.

The manufacturing method for the invented composition 2 is as follows.

Per 70 parts by weight of iron powder as an effective component (DKPmanufactured by Dowa Teppun K. K.) active carbon as carbon component(GL-50 manufactured by Noritto K. K.) in 10 parts by weight, common salt(sodium chloride) as a metal chloride in 2 parts by weight, tackifier(Metrose 60SH-4000 manufactured by Shin'etsu Kagaku K. K.) in 0.7 partsby weight, surface active agent (Metrose 60SH-4000 manufactured by KaoK. K.) in 0.2 parts by weight and sodium tripolyphosphate as pH adjusterin 0.1 part by weight are mixed and the resulting mixture is admixedwith water for its viscosity adjusted to be approximately 250,000 cps at20° C.

That is, active carbon, tackifier, surface active agent, pH adjuster,common salt and iron powder were added in this order and, moreover, inthe aforementioned mixing ratio, in a mixer (T. K. Hubismix 2P-100 typeand 100 liters by volume manufactured by Tokushu Kika Kogyo K. K.) andafter mixing for 5 minutes water was added in portions under stirringand thereafter kneading was continued for 15 minutes.

Thereafter, the blade and the vessel were cleaned and followed bymeasurement of viscosity and specific gravity. The water ratio wasadjusted in the following way until the viscosity of the mixture came tobe approximately 250,000 cps. The water ratio was 40 parts by weight per100 parts by weight of iron powder (DKP manufactured by Dowa Teppun K.K.). The viscosity of the resulting invented composition was 230,000cps.

The rate of revolution of the blade was kept at 10 rpm from the start tothe end of the test.

When his invented composition was kept at 10° C. for one hour, someincrease in viscosity was noted and the viscosity measured by thefollowing method after repeated kneading was 250,000 cps, and this waslaminated on the substrate 3 by screen printing.

In this case, too, the rate of revolution velocity of the blade was keptat 10 rpm from the start to the end.

The aforementioned viscosity is the result of measurement taken by theuse of a Viscometer BH-type manufactured by Tokimec Inc, and the rotor#7 with its revolving rate kept at 2 rpm, and the beaker's insidediameter was 85 φ mm as directed and the measuring temperature was 20°C.

The invented composition 2 being a fluid is small in specific surfacearea, this meaning less chance for contact with air and, furthermore,the possibility of contact with air of the iron powder is reduced by thepresence of free moisture and water-containing gel. The per-houroxidation volume is aggravated by lamination by the film or sheetcovering material and the oxidative reaction is almost retarded beforemanufacture of the exothermic device is completed.

Thus, the invented substrate is a fluid, this allowing laminationthereof on the upper surface of the water absorptive polymer-containingpolyester nonwoven fabric 3 a by screen printing and resulting in thepossibility of high-precision control of the laminated region. Moreover,it is now possible to control the layer thickness to be extremely smalland even uniform and it is even possible to prevent movement inside thepouch 1 through bondage of the nonwoven fabric 3 a of thewater-absorptive polymer-containing polyester blend to the inventedcomposition 2. Further, reduction of the layer thickness of the inventedcomposition 2 enables extreme thinning of the exothermic device.

In this embodiment the filmy substrate 130 mm wide is played out of aroll film at a horizontal speed of 180 m per minute, the upper surfacebeing meanwhile screen printed with the invented composition 2 to alayer thickness of approximately 0.5 mm. Immediately thereafter theprinted layer is covered with the covering material 4, this followed byheat-sealing the space outside the printed region and subsequent andsuccessive shearing along the sidewise center of the heat-sealed regionand extremely thin exothermic devices each thereof having a sealedmargin of L=7 mm along its periphery.

The individual sheared invented exothermic devices are then successivelyfed to the packing step for being sealed in gas-tight outer bags in anundisclosed way.

The invented composition 2 is printed on the upper surface of thesubstrate by a screen print. A part of the water contained is graduallyabsorbed therefrom and meanwhile the printed surface is covered by thecovering material 4. The time required for enclosure in the outer bag bysealing is extremely short after printing which is extremely short andthere is scarcely any likelihood of moisture being absorptive by thesubstrate to a degree for enabling the exothermic reaction.

There is scarcely any likelihood, either, of the invented composition 2starting generating heat in the manufacturing process, and there is norisk of occurrence of loss due to exothermic reaction or lowering of thequality of the exothermic composition. There is practically no risk ofthe invented composition being coagulated to cause dropping of theyield, and various known harms such as interruption of operation,limitation about working hours, difficulty and risk accompanyingcleaning of the machine or equipment, trouble of required frequentcleaning of the same or difficulty of treating or disposal of coagulatedmatters can be prevented.

When after the lapse of 24 hours the outer bag was broken and theuncovered normal exothermic device was stuck to the human skin, theexothermic temperature rose to approximately 38° C. in 1 to 2 minutesand thereafter the effect of heat generation was found controlling thetemperature in a range of 38° C. to 41° C. for more than 9 hours. Whilein use no movement of the invented composition 2 was noticed inside thepouch 1 and uniform generation of heat was noticed all over.

The invented exothermic device according to the second embodiment of thepresent invention, as shown in FIG. 2 in the schematic sectional view,has the invented composition 2 sealed in a rectangular flat pouch 130 mmlong and 95 mm wide, the bag 1 is formed of the non-gas-permeablesubstrate 3, the gas-permeable covering material 4 and in this case theexposed surface of aforementioned substrate 3 is covered with anadhesive layer 5 of styrene-isoprene-styrene block copolymer 100 μmthick.

The substrate 3, which is required to be sufficiently soft and flexible,is made of a core layer of polyethylene film of 40 μm thickness coveredon both sides of nonwoven fabric 3 a 3 c of rayon polyester blend of 140μm thickness having a rayon fiber content of 60% by weight.

The invented composition 2 and the adhesive layer 5 used in thisembodiment were the same as those used in the first embodiment.

The invented composition 2 was laminated on the upper surface of thesubstrate 3 by screen printing and, thereafter, the water absorptivelayer 6 (20 g/m² in METSUKE) was formed manually by scattering thewater-absorptive agent (highly water absorptive resin Aquaclic CS-6HSmanufactured by Nippon Shokubai K. K.) and then after covering the samewith the covering material 4 the peripheral margin was heat-sealed, andthe invented exothermic device having a he at-sealed margin L=7 mm widewas thus obtained.

In short, this second embodiment is essentially the same as the firstembodiment described above in the manufacturing method and otherconstitutional features, hence explanation about them will be omittedfor avoiding repetition.

The exothermic device referred to in this third embodiment is, as shownin the schematic sectional view of FIG. 3, essentially the same asdescribed above except that the vertical relationship between the waterabsorptive layer 6 and the invented composition 2 is reversed.

That is, in this exothermic device, the water absorptive layer is 6 of20 g/m² in specific basis weight was formed on the substrate 3 in thefollowing way.

That is, the water absorptive agent (highly water absorptive resinAquaclic CS-6HS manufactured by Nippon Shokubai K. K.) was used. Its 4%by weight aqueous solution was screen printed to a layer thickness of500 μm and was dried, thereby obtaining the water absorptive layer 6 of20 g/m² in a specific basis weight.

The invented exothermic device referred to in the third embodiment wasmade in the same way as described above except that the inventedcomposition 2 was formed on the surface of the water absorptive layer 6on the substrate 3.

After all, the manufacturing method and other constitutional featuresused was the same as embodiment 1 described above, its action andeffect, too, being the same, hence explanation about them will beomitted for avoidance of repetition.

The fourth embodiment of the present invention relates to an examplemade specifically adaptable to the shoulder made by the same method. Theperspective view of this exothermic device specifically for the shoulderis shown in FIG. 4.

The water absorptive substrate 3 is first screen printed with theinvented composition 2 in planar gourd shape as it is played out, thenthe exposed peripheral margin is coated with an adhesive and,thereafter, the covering material 4 is guided by a roller to belaminated thereon. Thus, the substrate 3 and the covering materials 4 issealed with the invented composition 2 enclosed therebetween, thisfollowed by formation of the adhesive layer 5 of 50 μm thickness on theexposed surface 1 of the substrate 3, the lengthy exothermic device thusobtained is extended by roll press to a size some 7 mm larger than theinvented composition 2 with its form adaptable to the desired part ofthe shoulder, in the planar gourd shape in this embodiment.

The substrate 3 and the covering material 2 are then stuck together alsoby the enclosed invented composition 2.

As shown in the sectional view of FIG. 5, water absorptive rayonnonwoven fabric 3 a approximately 80 g/m² in METSUKE is laminated withnon-gas-permeable polyethylene sheet 3 b approximately 50 μm thick andfor that the substrate 3 is so printed as to allow direct contact of theinvented composition 2 with one side of the rayon nonwoven fabric 3 a.

The aforementioned covering material 4 is of water absorptive rayonnonwoven fabric 4 a approximately 80 g/m² in MITSUKE laminated with agas-permeable polyethylene 4 b approximately 50 μm thick, itsgas-permeability being 300 g/m²24 hr. This covering material 4 has theinvented composition 2 laminated on the rayon nonwoven fabric 4 a so asto allow direct contact with the rayon nonwoven fabric 4 a.

The aforementioned adhesive layer 5 is formed ofstyrene-isoprene-styrene block copolymer. For improved adhesion hereofto the substrate 3, the exposed region of polyethylene sheet 3 b of thesubstrate 3 is roughened in advance by corona treatment with its wettingindex to be in excess of 40 dynes.

The invented composition 2 was prepared as follows: Mixed into 100 partsby weight of iron powder as an exothermic substance (DKP manufactured byDowa Teppun K.K.) were 0.21 parts by weight of water absorptive polymer(Sanwet IM-5000MPS manufactured by Sanyo Kasei K.K.) 1.4 parts by weightof tackifier (Celogen EP manufactured by Daiichi Kogyo Seiyaku K.K.),4.21 parts by weight of active carbon (SA-SUPER manufactured by NorittoK.KL.) 4.87 parts by weight of sodium chloride as a metal halide and0.25 parts by weight of sodium tripolyphosphate as a pH adjuster. Themixture was admixed with water so as to have its viscosity adjusted toapproximately 3,000,000 cps. at 20° C.

That is, the active carbon, the tackifier, the water absorptive polymer,the pH adjuster, the sodium chloride and the iron powder in the givenquantitative proportions thrown in this order into a mixer (T. K.Hybismix 2P-100 type, 100 liters by volume) and after stirring for 5minutes, a proper amount of water was added, this followed by kneadingfor 15 minutes.

Thereafter the blade and the casing were cleaned and after resumedkneading for 20 minutes viscosity measurement and measurement ofspecific gravity were made. The water ratio adjustment was done in thefollowing way so that the liquid's viscosity was adjusted toapproximately 3,000,000 cps. The water ration determined in this casewas 29.79 in parts by weight per 100 in parts by weight of the ironpowder (DKP of Dowa Teppun K. K.) and the viscosity of the inventedcomposition was 3,030,000 cps.

The blade's revolutional rate was kept at 10 rpm from start to end.

When the invented composition was kept for 1 hour at 10° C., some risein viscosity was noted but after resumed kneading the viscosity measuredin the following way was 3,050,000 cps and this was laminated on thesubstrate 3 by screen printing.

In this case, too, the blade's revolutional rate was kept at 10 rpm fromstart to end.

The viscosity was measured by the use of R110 type viscosimeter, RE 11OUsystem, Detection Head RE100U and Controller RC100A manufactured by TokiSangyo K. K. and the rotor used was of SPP type with its revolutionalrate kept at 0.2 rpm. (D=0.4 (1/S) ) and measurement was taken at 20° C.

Hence, in this invented composition 2, free moisture or moisture presentin the water-containing gel functions as a barrier, thereby retardingexothermic reaction almost totally.

When the invented composition 2 is screen printed on the substrate 3 toa layer thickness of 820 μm, the free moisture in the inventedcomposition and moisture present in the water-containing gel aregradually absorbed by the water absorptive rayon non-woven fabric 3 aand, further, after placing of the covering material 4 they are alsoabsorbed by the rayon nonwoven fabric 4 a and in time the amount ofwater within the exothermic composition 2 becomes optimum for creatingthe predetermined exothermic temperature.

While it takes rather a long time for the free moisture and moisturepresent in the water-containing gel to be absorbed by the substrate 3and the covering material 4 so that the water ratio becomes optimum, thetime required for the manufactured invented exothermic device to beenclosed or sealed in a non-gas-permeable pouch is extremely short, andthere is no possibility of the water ratio of the invented composition 2coming to be optimum for a rise of the exothermic temperature to thepredetermined level.

Thus, there is no possibility of the invented composition 2 to generateheat before enclosing the exothermic composition in a non-gas-permeablepouch and there is no risk of the various known harms caused bycoagulation of the product of exothermic reaction such as lowering ofthe yield, handling difficulty, complicated machine maintenance,limitations about the machine's operating hours and worker's workinghours and difficulty of treating of or disposal of the coagulants.

Since the excessive moisture present in the invented composition 2 isabsorbed by the water absorptive rayon nonwoven fabric 3 a of thesubstrate 3 and the water absorptive rayon nonwoven fabric 4 a of thecovering material 4 so that the mix ratio of water will have come downto the optimum level for the predetermined exothermic temperature(reaction) by the time it reaches an end user, there is no possibilityof deterioration of the invented composition 2 before the outer bag istorn and the invented exothermic device is taken out for contact withair. Thus, the quality of the invented composition 2 is retainable at ahigh level and when the bag is torn and the exothermic device is takenout, the exothermic reaction is initiated immediately for quick rise ofthe temperature to the predetermined level.

Moreover, the invented composition 2 has high fluidity and therefore canbe laminated on the substrate 3 by such techniques as printing orcoating; hence, when compared with the conventional powdery exothermiccompositions which have no fluidity at all and are simply dropped ontothe substrate 3, it is uniformly laminated in the predetermined regionat a higher rate of speed with great accuracy.

When the aforementioned invented exothermic device was enclosed in anon-gas-permeable bag, and after lapse of 10 days, it was taken out ofthe bag torn open and then stuck to the skin of the shoulder, excellentwarming effect was retained for more than 5 hours.

With regard to applicability of the invented exothermic device, theextreme thinness of the exothermic device makes it as a whole soft andflexible and mild in feel to the skin of the shoulder, it was readilydeformable according to curvature of the shoulder, also well followingthe movement of any part of the shoulder, excelled in adherence where itis used, hence is no risk of peeling off during use, excelled in warmingeffect and effective for warming, among others, the shoulder.

While in use, the exothermic composition 2 does not move noticeably, thedistribution of the exothermic temperature is uniform, there is no riskof low-temperature burn and improved safety is in use.

Then, the invented exothermic device for the back as embodiment 5 wasmanufactured in the same way as the fourth embodiment in a wayunillustrated but similar to the fourth embodiment.

The invented composition 2 was prepared as follows: To 100 parts byweight of iron powder as an exothermic composition (GFP manufactured byDowa Teppun K. K.), the following ingredients were added: 7.0 parts byweight of an active carbon (SA-SUPER manufactured by Noritto K.K.), 2.0parts by weight of a diatomaceous earth (oblite) as a water retainer,1.4 parts by weight of a tackifier (Celogen EP manufactured by DaiichiKogyo Seiyaku), 0.3 parts by weight of a water-absorptive polymer(Sanwet IM-5000MPS manufactured by Sanyo Kasei K.K.), 5.0 parts byweight of a sodium chloride as a metal halide, and 0.3 parts by weightof a sodium tripolyphosphate as pH adjuster. The mixture was then addedwith water so that the viscosity became 2,500,000 cps at 20° C.

Specifically, the active carbon, the diatomaceous earth, the tackifier,the water adsorptive polymer, the pH adjuster and the sodium chloridewere put in a mixer (T. K. Hybismix 2P-100 type, 100 liters by volume)in this order and in the above proportions. Then, the lid was closed soas to secure the mixer air-tightness. Then, while the mixture wasstirred at 10 rpm, measurements on viscosity and specific gravity wereconducted., the iron power was put into the mixer and stirred for 3minutes. Water was then added while the mixture was still being stirred.then, the rate of revolution was raised to 15 rpm and the mixture wasfurther mixed for about 5 minutes. The mixing was then stopped.

Thereafter, the blade and the casing were cleaned and after resumedmixing for 5 minutes at 1 rpm measurements on viscosity and specificgravity were conducted. The water ratio (proportion) adjustment was donein the following way so that the viscosity became around 2,500,000 cps.The water ratio determined in this case was 42.0 in parts by weight per100 parts by weight of iron powder (DKP manufactured by Dowa TeppunK.K.). The specific gravity of the invented composition was 2.428 g/mland the viscosity was 2,520,000 cps.

When the invented substance was kept for 1 hour at 10° C., some rise inviscosity was noted but after resumed kneading the viscosity measured inthe following way was 2,550,000 cps, and this was laminated on thesubstrate 3 by screen printing.

In this case, too, the blade's revolutional velocity was kept at 10 rpmfrom start to end.

The viscosity was measured by the use of R110 type viscosimeter, RE 110Usystem, Detection Head RE100U and Controller RC100A manufactured by TokiSangyo K. K. and the rotor used was of SPP type with its revolutionalvelocity kept at 0.2 rpm (D=0.4 (1/S) ) and measurement was taken at 20°C.

Hence, in this invented composition 2, free moisture or water present inthe gel serves as a barrier, thereby retarding the exothermic reactionalmost totally.

When the aforementioned invented exothermic device was enclosed in anon-gas-permeable bag, and after lapse of 10 days, the inventedexothermic device was taken out and then stuck directly to the skin ofthe back by using the adhesive layer 5.

Excellent warming effect was noted for more than 6 hours.

With regard to applicability of the invented exothermic device, theextreme thinness of the exothermic device makes it as a whole soft andflexible and mild in feel to the skin, readily deformable according tocurvature of the shoulder also well following its movement, excelled inadhesion to where it is used, there is no risk of peeling off duringuse, excelled in warming effect and effective for warming, among others,the back of the body.

While in use, the exothermic composition 2 does not move noticeably, thedistribution of the exothermic temperature is uniform, hence there is norisk of low-temperature burn and improved safety is in use.

Another exothermic warming experiment was then made in the followingway.

Iron powder (DKP manufactured by Dowa Teppun K. K.) in 70 parts byweight, active carbon as carbo component (GL-50 manufactured by NorittoK.K.) in 10 parts by weight, sodium chloride as a metal chloride in 2parts by weight, tackifier (Metrose 60SH-4000 manufactured by Shin'etsuKagaku K.K.) in 0.7 parts by weight, surface active agent (Demol EPmanufactured by Kao K. K.) in 0.2 parts by weight and pH adjuster(sodium tripolyphosphate) in 0.1 part by weight were mixed with additionof an excessive amount of water. Two kinds of fluids were prepared whoseviscosities were 10,000 cps and 6,800,000 cps in viscosity respectivelyat 20° C.

An experiment was made using two specimens of the invented compositions10,000 cps and 6,800,000 cps respectively.

The invented composition was put in a 2001 beaker 10, and, as shown inFIG. 6, two temperature sensors were configured in such a way that oneof them was placed at the surface and the other one was at the location10 mm below the center of the surface (position D) so as to measure thetemperature difference.

The result showed that, with the specimen 10,000 cps in viscosity therewas scarcely noted any rise in temperature within approximately 20minutes either in the surface or beneath the center of the surface, withthe other specimen 6,800,000 cps in viscosity rise in temperature wasnoted in the surface after approximately 5 minutes, but rise intemperature was scarcely noticeable then beneath the center of thesurface.

Meanwhile, a comparative experiment was made using an exothermiccomposition comprising iron powder 60 in parts by weight, 10% by weightof table salt solution in 25 parts by weight, active carbon in 13 partsby weight and wood flour 14 in parts by weight, the iron powder, tablesalt and the active carbon being the same as used in the aforementionedembodiment.

With this composition, however, a viscosity measurement was performed.

In the comparative experiment made using this specimen, rise intemperature was noted almost instantly in the surface as well as beneaththe center of the surface and in some cases the temperature was seenexceeding 60° C. after some 2 minutes.

In the present invention, the above described embodiments may becombined properly but also preferred is application of a film or thinsheet of water absorptive materials such as highly water absorptivepaper to either or both sides of the invented composition, this beingeffective in two ways, i.e., absorption of a part of water or vapor bysuch paper and a more secure adhesion of the invented compositionthereto.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A method of manufacturing an exothermic device comprising the stepsof applying a fluid exothermic composition on a film or sheet substrateto form a laminate, said exothermic composition having a viscosity inthe range of 1,000 to 7,500,000 cps at 20° C., stamping the resultinglaminate into desired shapes, and applying a gas permeable covering toat least one side of the laminate prior to or following the stampingstep.
 2. A method defined in claim 1 further comprising the steps ofapplying two layers of film or sheet one to each side of the stampedlaminates, the two layers of film or sheet being larger than the stampedlaminates and extending outwardly therefrom, stamping the two layers offilm or sheet, with the exothermic sheet interposed therebetween, at alocation spaced from the edge of said laminate, and simultaneously withstamping or after stamping sealing said two layers of film or sheetextending outwardly from the interposed exothermic sheet.
 3. The methodof manufacturing an exothermic device as defined in claim 1, wherein atleast one side of the fluid exothermic composition is sealed with a filmor sheet of water absorbing material.
 4. The method defined in claim 1,wherein the viscosity of the fluid exothermic composition is within therange of 50,000 to 6,500,000 cps at 20° C.
 5. The method defined inclaim 4 further comprising the steps of applying two layers of film orsheet one to each side of the stamped laminates, the two layers of filmor sheet being larger than the stamped laminates and extending outwardlytherefrom, stamping the two layers of film or sheet, with the exothermicsheet interposed therebetween, at a location spaced from the edge ofsaid laminate, and simultaneously with stamping or after stampingsealing said two layers of film or sheet extending outwardly from theinterposed exothermic sheet.
 6. The method of manufacturing anexothermic device as defined in claim 4, wherein at least one side ofthe fluid exothermic composition is sealed with a film or sheet of waterabsorbing material.